zyewdall Posted February 6, 2010 Share Posted February 6, 2010 A friend's car... I haven't looked at it person yet, but she says it revs up to 4 or 5000rpm randomly and often, and also overheats quickly (I suspect unrelated, probably a blown coolant hose lost the coolant, as she said it was leaking more coolant and oil recently (oil is the front cam seals or oil pump seals (no TOD though) I think..., plus the power steering pump. I did some work on it a few months ago, all new ignition parts and it ran much better after that. I did notice the temperature spike once back then -- bad thermostat was suspected, which I replaced. Any ideas on what would make an SPFI rev up like this (other than a stuck throttle cable... which is not completely out of the question) About 260k on it, and it's on it's last legs in alot of ways but I want to get it running enough to get it back to my place (about 50 miles including 4000 feet elevation gain) where it can be a parts car, instead of where the city's going to tow it at her place. Or... if it's a really easy fix... just fix it. Link to comment Share on other sites More sharing options...
nipper Posted February 6, 2010 Share Posted February 6, 2010 I would start with all the obvious things first, like vacume hoses, cracked vacume fittings etc. I know what would make an RPM drop, but for the life of me i cant remeber what would do it on a SPFI. nipper Link to comment Share on other sites More sharing options...
zyewdall Posted February 7, 2010 Author Share Posted February 7, 2010 I would start with all the obvious things first, like vacume hoses, cracked vacume fittings etc. I know what would make an RPM drop, but for the life of me i cant remeber what would do it on a SPFI. nipper That's whats getting me too... all of my theories apply to carbed vehicles but not SPFI... injector sticking open sometimes maybe? Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 7, 2010 Share Posted February 7, 2010 For it to get to 5k you need the throttle plate open - no amount of extra fuel will do it without the air for it to mix with. It's got to be a mechanical bind of some kind as it would never get that out of control without the air supply from the TB. Only other thing I can think of would be a sticking idle air control valve - but even then I wouldn't think it could get to 5 grand. GD Link to comment Share on other sites More sharing options...
nipper Posted February 7, 2010 Share Posted February 7, 2010 I don't think so. I would go with a bad emission control of some kind. Something leans out the mix, then something compensates, then it revs, and the cycle is back again. ANother possability, a bad O2 sensor? that would fit. nipper Link to comment Share on other sites More sharing options...
zyewdall Posted February 14, 2010 Author Share Posted February 14, 2010 Well.... I went and looked at it today. It's leaking coolant out of the water pump (I think... coming out of the bottom of the timing cover). steady drip drip... that explains the overheating. When filled back up it does not overheat (until it runs out of coolant again, of course). We got it about 30 miles back towards my house. It did not do the revving thing for me... it does, however, run terrible. Won't start unless you give it gas, unlike most fuel injected ones I've had, and idles very low till it warms up. And, it just doesn't sound right -- some extra mechanical noise that I'm not using to hearing I think.. maybe disintegrating water pump? Runs pretty nice at higher rpms on the highway though, with normal power. Just bad at idle. Wonder if some seafoam would help it... this one is really holding up the bad reputation of EA82's, unlike other EA82's I've had that always ran great. Anyway... should make it the rest of the way back to my place in the next few days, and then I can have more time to poke at it and diagnose problems. Link to comment Share on other sites More sharing options...
CHIM Posted February 14, 2010 Share Posted February 14, 2010 Most fuel injetion systems give very little priority to the O2 at an idle, usually somwhere around 8% swing AFR wich shouldn't couse an idle as high as your describing. I would think it's not the O2 sensor. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted February 14, 2010 Share Posted February 14, 2010 (edited) I don't think so. I would go with a bad emission control of some kind. Something leans out the mix, then something compensates, then it revs, and the cycle is back again. 5k RPM is a lot of air-flow. Engine's are just air pumps. Where is the air comming from if the throttle is closed? The throttle opens one way and one way only on the SPFI - with the accelerator cable. It's all well to consider other possibilities like the idle air control valve - but I've never had one rev up that hard. 1500 - sure. 2500...... *maybe*. 5000 - no es beuno. I would have to experiment with it to see if it's even possible but my gut reaction is that it's not - at least within the bounds of how much air the IAC can provide through it's little hole under the throttle body. I've had them malfunction and the idle does get higher but not by 4 grand. It just can't suck that much through it's 1/2" ID drinking straw of an air supply line. GD Edited February 14, 2010 by GeneralDisorder Link to comment Share on other sites More sharing options...
zyewdall Posted February 14, 2010 Author Share Posted February 14, 2010 (edited) I remain skeptical that it ever did the revving quite as described.... it never did it for me, and idling very LOW rpm is more the issue that I'm seeing... as in so low that it won't start unless you rev it with the accelerator. Which, could also be the idle air control valve, and maybe it did stick open at some earlier time and make it rev somewhat and now it's stuck closed..... I did see a bit of oil deposits in the intake, so it could be a bad pcv cycling oil back up there and gumming stuff up perhaps? Edited February 14, 2010 by zyewdall actually looked at the car and have first hand observations now :) Link to comment Share on other sites More sharing options...
Ever Victorious Posted February 14, 2010 Share Posted February 14, 2010 Still, thoroughly inspect and adjust the throttle cable, make sure anything there that needs to be lubricated is. I've had a throttle cable stick for a few seconds on an old American V8 before, it's scary as hell... Link to comment Share on other sites More sharing options...
roostema4328 Posted February 14, 2010 Share Posted February 14, 2010 fuel injected vehicles sometimes rely heavily on the coolant temp sensor for fueling determination. If your coolant is low from the leaking water pump. You may have nothing wrong other than that. I would fix the leaking water pump. You could have an air bubble at the coolant temp sensor. Those sensors dont read air temp very well. It could be changing the air/fuel ratio on you intermittently. Link to comment Share on other sites More sharing options...
CHIM Posted February 15, 2010 Share Posted February 15, 2010 fuel injected vehicles sometimes rely heavily on the coolant temp sensor for fueling determination. If your coolant is low from the leaking water pump. You may have nothing wrong other than that. I would fix the leaking water pump. You could have an air bubble at the coolant temp sensor. Those sensors dont read air temp very well. It could be changing the air/fuel ratio on you intermittently. Reading colder tahn it accully is would cause the ECU to richen the mixture, but still wouldn't rev without extra air. Link to comment Share on other sites More sharing options...
roostema4328 Posted February 15, 2010 Share Posted February 15, 2010 well the funny thing is that it also affects the idle control circuit too. The ecu uses the coolant temp info for cold idling/high idle. so if air bubbles go by the idle could surge and drop intermittently. Link to comment Share on other sites More sharing options...
Speedwagon Posted March 24, 2011 Share Posted March 24, 2011 (edited) I'm bumping this thread, because the problem followed the SPFI system. I got the car this thread was started about, and put the SPFI system on my Brat. Problem is still occuring. The ECU flashes a code 24(all the time while the vehicle is on). I swapped out the CTS, IAC and TPS with spares, still happens. When it starts to go nuts, I can bring it down to near idle by tapping the gas pedal. Once it gets down to around 1500 rpms, it jumps back up to ~4k. If I keep blipping the throttle, I can keep it jumping up and down between 1-2k though. Also, when the vehicle is cold and started, it doesn't seem to happen. But if I shut it off, walk away, and come back a short time later, when I start it up it starts doing this right away. Won't start unless you give it gas, unlike most fuel injected ones I've had, and idles very low till it warms up. Still does this too. Though I can often get it to start without gas applied, but it stalls right away. Edited March 24, 2011 by Speedwagon Link to comment Share on other sites More sharing options...
Speedwagon Posted March 25, 2011 Share Posted March 25, 2011 Ok, while the engine was cold just a few minutes ago, I started it and then disconnected the IAC. No change whatsoever. I verified the IAC works(applied 12v manually, watched it move). I saw 12v on one of the wires feeding the IAC though, so how exactly does this thing switch on and off? Maybe the 12v supply is dead shorting somewhere? Is that a switched 12v, or switched ground? Link to comment Share on other sites More sharing options...
MilesFox Posted March 25, 2011 Share Posted March 25, 2011 I would recommend: Throttle cable may have stuck. do the lubrication, look for frays. freak occurence. bad idle and starting may be a bad coolant temp sensor, compoinded by low coolant and overheat, may be stretched and innacurate. Replace the water pump definitely if if it is leaking. It may just be the water pipe o-ring instead. the o-ring is easy to fix, one 10mm bolt is all it takes. Otherwise, do the water pump and cam seals, timing belts, all at the same time if you have all the parts. the high idle can be compounded by a bad coolant temp sensor, and the car thinks it's cold, and holds the IAC open. possible stuck IAC due to carbon. Try sea foam in the IAC itself. If you have the resources, pull the engine and do all the sals, get the gasket kit. Beware that the overheat may preclude a bad head gasket. just get the entire gasket set, and take the time to refresh the engine. Link to comment Share on other sites More sharing options...
Speedwagon Posted March 25, 2011 Share Posted March 25, 2011 (edited) I would recommend: Throttle cable may have stuck. do the lubrication, look for frays. freak occurence. bad idle and starting may be a bad coolant temp sensor, compoinded by low coolant and overheat, may be stretched and innacurate. Replace the water pump definitely if if it is leaking. It may just be the water pipe o-ring instead. the o-ring is easy to fix, one 10mm bolt is all it takes. Otherwise, do the water pump and cam seals, timing belts, all at the same time if you have all the parts. the high idle can be compounded by a bad coolant temp sensor, and the car thinks it's cold, and holds the IAC open. possible stuck IAC due to carbon. Try sea foam in the IAC itself. If you have the resources, pull the engine and do all the sals, get the gasket kit. Beware that the overheat may preclude a bad head gasket. just get the entire gasket set, and take the time to refresh the engine. I don't think you are following me: I moved the SPFI components over to my EA81. Water pump isn't a problem, neither is coolant level. There is no overheating on the EA81. Throttle cable is fine, it never did this with the carb on it(and I did check it to verify). I already swapped the IAC, TPS, and CTS. Problem still exists. I'm bumping this thread, because the problem followed the SPFI system. I got the car this thread was started about, and put the SPFI system on my Brat. Edited March 25, 2011 by Speedwagon Link to comment Share on other sites More sharing options...
Deener Posted March 25, 2011 Share Posted March 25, 2011 I have had a low rough idle issue on my 88GL SPFI and I went down the road of suspecting the TPS, and the IAC but it was in fact the CTS in the end for me...twice. Exactly as you describe - won't start unless you floor the throttle and runs like cr@p at idle but was fine at high RPM...note that it would sort of 'stumble' start but only after cranking it for longer than normal with the pedal all the way to the floor. You are getting power to the CTS and resistance from the sensor, correct? You have tested and ruled out vaccuum leaks too, right (especially at the intake gaskets)? No idea what would cause the idle to jump that high though. Link to comment Share on other sites More sharing options...
Speedwagon Posted March 25, 2011 Share Posted March 25, 2011 I have had a low rough idle issue on my 88GL SPFI and I went down the road of suspecting the TPS, and the IAC but it was in fact the CTS in the end for me...twice. Exactly as you describe - won't start unless you floor the throttle and runs like cr@p at idle but was fine at high RPM...note that it would sort of 'stumble' start but only after cranking it for longer than normal with the pedal all the way to the floor. You are getting power to the CTS and resistance from the sensor, correct? You have tested and ruled out vaccuum leaks too, right (especially at the intake gaskets)? No idea what would cause the idle to jump that high though. So you have 2 CTSs bad on you, in a row? I tested the CTS under the faucet, and resistance changes as the water warmed up. I didn't check for power though. Vacuum and intake leaks are highly unlikely, since I move the entire SPFI unit from one motor to another, with the same results. And I checked and rechecked to make sure I had connected everything correctly. Link to comment Share on other sites More sharing options...
Deener Posted March 25, 2011 Share Posted March 25, 2011 So you have 2 CTSs bad on you, in a row? I tested the CTS under the faucet, and resistance changes as the water warmed up. I didn't check for power though. Vacuum and intake leaks are highly unlikely, since I move the entire SPFI unit from one motor to another, with the same results. And I checked and rechecked to make sure I had connected everything correctly. No the sensors were actually broken right under the rubber, right where it meets the bolt piece. In both cases one of the wires had snapped as they sink into the solder but I couldn't tell it was broken until I peeled the rubber back (most likely broke them due to high tension/short wire plus fiddling around in the Tstat housing area). Sounds like your sensor is working though if your resistance values change with the temp, with a broken wire you get zero. The reason I suggested a possible intake gasket leak is because of the coolant loss + rough idle. If you have isolated the coolant leak to the water pump then that theory doesn't apply. I would still check the vaccum points just to be 100% sure that something wasn't accidentally missed. My favorite move is the carb cleaner shot directly onto the hoses/intake etc because when the RPM increases, the breach point is obvious. Timing belts are good and tight too? Belt slop gave me poor all round performance too but rough idle for me was always a vaccum leak or the CTS. Link to comment Share on other sites More sharing options...
Speedwagon Posted March 25, 2011 Share Posted March 25, 2011 (edited) No the sensors were actually broken right under the rubber, right where it meets the bolt piece. In both cases one of the wires had snapped as they sink into the solder but I couldn't tell it was broken until I peeled the rubber back (most likely broke them due to high tension/short wire plus fiddling around in the Tstat housing area). Sounds like your sensor is working though if your resistance values change with the temp, with a broken wire you get zero. The reason I suggested a possible intake gasket leak is because of the coolant loss + rough idle. If you have isolated the coolant leak to the water pump then that theory doesn't apply. I would still check the vaccum points just to be 100% sure that something wasn't accidentally missed. My favorite move is the carb cleaner shot directly onto the hoses/intake etc because when the RPM increases, the breach point is obvious. Timing belts are good and tight too? Belt slop gave me poor all round performance too but rough idle for me was always a vaccum leak or the CTS. Once again: the spfi was swapped to a different engine(to an EA81). The water pump is not an issue. The only issue is the engine rpms. I appreciate the help you guys are taking the time to provide, but you don't seem to be reading the complete thread here. I've stated this a few times. Now, I have isolated the problem to the IAC. I just went to the store, shut off the car. When I came back out and started the car, it started screaming right away. I went under the hood, and disconnected the IAC. The idle immediately returned to normal. It seems to me that the IAC is operating reverse to what it should be... but why? Edited March 25, 2011 by Speedwagon Link to comment Share on other sites More sharing options...
Caboobaroo Posted March 25, 2011 Share Posted March 25, 2011 Well I don't have any ideas as they've already been mentioned (CTS, IAC, TPS) but when I get home, I'll see about digging out my '87 FSM and see if I can come up with anything. Might be a good idea to go to the junkyard and snatch up another ECU just for s&g's though.... Link to comment Share on other sites More sharing options...
Speedwagon Posted March 25, 2011 Share Posted March 25, 2011 (edited) Well I don't have any ideas as they've already been mentioned (CTS, IAC, TPS) but when I get home, I'll see about digging out my '87 FSM and see if I can come up with anything. Might be a good idea to go to the junkyard and snatch up another ECU just for s&g's though.... And on that note: it was just doing 5 rapid flashes at me, over and over, with the key in the on position. Any idea what that means? edit: Someone should add a note to the ECU codes guide that when the ECU gives out only short flashes (5-7 of them I think?) that it means there are no stored/current codes. So, the problems are now gone? Interesting... I'll just have to keep driving it, and see if the problem occurs again. Edited March 25, 2011 by Speedwagon Link to comment Share on other sites More sharing options...
MilesFox Posted March 26, 2011 Share Posted March 26, 2011 And on that note: it was just doing 5 rapid flashes at me, over and over, with the key in the on position. Any idea what that means? edit: So, the problems are now gone? Interesting... I'll just have to keep driving it, and see if the problem occurs again. This would be an identity code. i dont know what it is off hand, but it is listed in the haynes book. it will tell you if the car is spfi, mpfi, mt, at, lower 48 or cali. it will correlate with the donor car the ecu came from Link to comment Share on other sites More sharing options...
Speedwagon Posted March 26, 2011 Share Posted March 26, 2011 Ah hah! Wiring gremlins! I just did a continuity test from pin 45 of the ECU, to various parts along the harness. There is continuity from pin 45 to the engine bay plug, on both sides of the plug. There is not continuity to the end of the engine harness for the IAC wire that correlates to pin 45. Since the plastic wire loom is basically falling apart, I think it is safe to say I will encounter more problems if I keep this harness, rather than try to get a new one at the junkyard in better condition. Link to comment Share on other sites More sharing options...
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