TPS, IAC, or something else?

[toadleyb]

Hey all, I have an 87 DL wagon EA82 SPFI. I have had it about 3 years and it has run like a champ up until recently. It doesn't get driven much in the summer. I just started driving it on a regular basis in the last week or so.

 

The problem I am having is this. When I start it on a cold day it starts hard and I have to keep feathering the accelerator to keep it running for the 1st 2 to 3 minutes. Once I get it to stay running it will keep surging like someone is sitting in the car hitting the accelerator. If I don't let it warm up for a long period of time it will bog bad when I step on it but then all of a sudden kick up to a really fast idle and take off on me!

 

I have done some reading about the TPS and IAC. Could one of these be the culprit? If so is there a way to clean them or do they need to be replaced?

 

Thanks for any help anyone can offer.

[GeneralDisorder]

Could be a lot of things, but I would be checking the Coolant Temp Sensor and it's plug followed by a good IAC cleaning.

 

Both can cause temperature related problems.

 

TPS shouldn't be temperature related.

 

My money is on the CTS being faulty or the plug corroded.

 

Check for ECU codes too.

 

GD

[toadleyb]

Thanks for the reply. Where is the CTS located?

 

Todd

[GeneralDisorder]

It's near the thermostat housing on the manifold. Should be a 17 or 19mm with a two-blade connector.

 

GD

[toadleyb]

I found the CTS and cleaned the connectors. My car has the CTS with the pigtail attached. This didn't help at all.

 

I just did a diagnostic check and I am getting 8 different error codes. These are the codes I am getting

 

21 - CTS

24 - Air control valve

31 - TPS

32 - O2 Sensor

34 - EGR solenoid

35 - Purge control Solenoid valve

42 - Idle Switch

51 - Neutral Switch

 

Is it really possible all of these things are bad or could one or more be causing others?

 

Anybody wanna buy an 87 DL wagon???

 

Todd

[Skip]

Howdy Todd,

You ask

"could one or more be causing others?"

 

Answer is maybe, the problems you have had could be

setting "ghost" codes.

 

Try clearing the codes* and checking them again as

soon as you get a CEL

(*info for this procedure is in the USRM)

 

The cleaning of the contacts that GD mentions is mainly for the MPFI units.

Their CTS contacts get corroded from being in a

"well" where water tends to collect.

Your SPFI unit does not have this type of connection

as you correctly state.

 

You problem is probably related to the IAC.

But you could also have other problems.

The ECU is your friend in these endeavors.

 

The Idle Air Control (IAC) valve is

mounted on the front of the throttle body, this

unit is known for gumming up and causing

idle issues just as you describe.

 

It should be cleaned at regular intervals.

There are several methods -> all can be found by searching

 

Note: the search function needs four letter words or the use of the wild card *

e.g. IAC* not just IAC

 

The CTS in your case can be easily tested as it is a

variable resistance.

The chart for these resistances vs temp can be found

also by searching.

 

If you have problems finding these articles please ask

for assistance.

Hope this helps.

[Gloyale]

Several of those can be false codes. And others could be triggered by the effects of running crappy off bad data from a failed CTS.

 

Did you test the resistance of the CTS? Resistance should be around

2-3k Ohms at 68 degreesF. Higher resistance if colder, up to 11k ohms

resistance should drop as the engine warms up. Down to between 200-500 ohms hot.

 

Basically anything other than Zero Ohms or Infinite, and change that correponds to temp, means it's good. If not replace it.

 

I would ignore codes 32 thru 51 for now. They are not likely the problem. Only others that are troubleing are the TPS code and the Air Control Valve.

 

But for now, Lets test the CTS, confirm it as good or get it replaced. Then clear the Codes(hook up both stes of connectors, start car, run it for 40 seconds, til the CEL blinks) and then see what still comes up in D check(just greens)

 

Next test is the TPS though.

[toadleyb]

Thanks for the response. I am done fighting with it for now. Been playing for 3 or 4 hours and it is stinking cold and wet outside. I just took apart the IAC and cleaned it up with some brake clean. Didn't seem to help any.

 

I will try your recommendations later and post back. I have a bunch of errands to run. Will see how the car runs.

 

Thanks

 

Todd

 

PS I forgot to mention at no time during all of these problems has the CEL come on.

[azsubaru]

Did you say the CEL has not been on at all - and you have 8 different errors? It should be on. maybe it's burnt out.

 

I think you should first clear the codes and wait for the error to show up again on the ECU, otherwise you're just guessing and it sounds like you've done enough of that self abuse already.

 

The idle switch might be a possiblity, either dirty/bouncy or could just need adjustment.

[Gloyale]

The idle switch might be a possiblity, either dirty/bouncy or could just need adjustment.

 

+1 for this

 

It was my next though after the CTS

 

But for sure make sure the CEL is working, clear codes, start over, after each repair or adjustment.

[notliving]

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Edited November 28, 2010 by notliving