carfreak85 Posted August 16, 2022 Share Posted August 16, 2022 (edited) 1999 automatic EJ253. Plugs (NGK), wires (OEM) and front oxygen sensor (OEM) replaced in the last two years. For many years we've had what I can best describe as a tiny "hiccup" when pulling away from a stop. Used to do it immediately after shifting into 2nd gear, and was hardly noticeable to anyone but myself. Sometimes it will take a few extra revolutions compared to "normal" to start the engine. It's gradually become worse, to the point of having multiple misfires when tipping into the throttle while pulling away from a stop. Full throttle seems to bypass the problem. The check engine lamp has never illuminated during or after one of these misfire events. Based on research here and on SubaruForester.org I replaced the front oxygen sensor last week, and while the problem has improved a little bit, it's still there and still annoying. What am I missing here? Need to clean/replace the MAF sensor? Rear oxygen sensor? Edited August 18, 2022 by carfreak85 Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted August 16, 2022 Share Posted August 16, 2022 live data could help here. I will say, a '99 could have a bad knock sensor. If this car has a MAF, it may be bad/intermittent..... Link to comment Share on other sites More sharing options...
carfreak85 Posted August 16, 2022 Author Share Posted August 16, 2022 (edited) Knock sensor is OEM and isn't any older than a few years (replaced last HG go-round). Going to clean the MAF and check for vacuum leaks in the inlet system this afternoon. Edited August 16, 2022 by carfreak85 1 Link to comment Share on other sites More sharing options...
carfreak85 Posted August 18, 2022 Author Share Posted August 18, 2022 Cleaning the MAF did nothing. Link to comment Share on other sites More sharing options...
el_freddo Posted August 22, 2022 Share Posted August 22, 2022 Is this a conversion or an EJ251? I didn’t think the EJ253 came in until c2004/5 Actually thinking about it this is DOHC if it’s got a MAF, meaning it’s an EJ25D. My initial thoughts (being for an EJ253 with the variable valve timing) was those little idle butterfly things being the issue if the NA models had them fitted. If it is an EJ251 I’d be looking into its crappy IACV that’s a plunger plug design. It could be gummy or the rubber on the plunger cracked/worn, effecting the air fuel ratio enough to upset the ignition in the cylinder momentarily as the ECU sorts out the mixture from idle to load throttle. The IACV could also be having issues if it’s the EJ25D, but from memory this IACV design is the same or ver similar to the phase EJ22 rotating valve design. Either of these IACVs not operating properly may not throw a CEL or store a code. I know this post is a bit all over the shop, I’m trying to cover all bases to save time at your end as I’m sure you don’t have an EJ253 unless it’s a conversion. Cheers Bennie Link to comment Share on other sites More sharing options...
carfreak85 Posted August 22, 2022 Author Share Posted August 22, 2022 It's a USDM 1999 with a non-AVCS EJ253 SOHC engine (build plate on strut tower confirms -253 engine). IACV may be my next target. 1 Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted August 22, 2022 Share Posted August 22, 2022 throttle body clean? Link to comment Share on other sites More sharing options...
heartless Posted August 22, 2022 Share Posted August 22, 2022 (edited) 4 hours ago, carfreak85 said: It's a USDM 1999 with a non-AVCS EJ253 SOHC engine (build plate on strut tower confirms -253 engine). IACV may be my next target. interesting that your 99 has a 253... i had an 02 with a 251 and my 04 has a 251, but the 05 parts car is a 253 (all three Foresters) curious if the vin number on the strut tower and the one in the dash are the same? How long have you owned this car? edit to add... interesting little tidbit - had no idea... (from vehiclehistory.com) "The Forester used the EJ25D from 1997 to 1998, then switched to the EJ251 from 1999-2004, the EJ253 in 1999 and again from 2005-2010, the EJ254 from 1998-2002 in the T25 version and from 2004-2020, the EJ255 from 2004-2013 and the EJ257 from 2004-2005 in the XT trim." Edited August 22, 2022 by heartless Link to comment Share on other sites More sharing options...
el_freddo Posted August 23, 2022 Share Posted August 23, 2022 Good find @heartless! I never knew that. So you’ve got a real odd ball variant there @carfreak85… I thought the L series was the black sheep of the family but this model is out there! So this EJ253 - does it have the variable valve timing and the idle butterfly setup just above the inlet ports on the head? I’ve heard these can give trouble if you have them. Can you do a smoke test for vacuum leaks? Cheers Bennie Link to comment Share on other sites More sharing options...
carfreak85 Posted August 23, 2022 Author Share Posted August 23, 2022 19 hours ago, heartless said: curious if the vin number on the strut tower and the one in the dash are the same? How long have you owned this car? Yes, VINs match. Vehicle has been in our family since ~2004 (or two sets of HGs ). 3 hours ago, el_freddo said: So this EJ253 - does it have the variable valve timing and the idle butterfly setup just above the inlet ports on the head? I’ve heard these can give trouble if you have them. Can you do a smoke test for vacuum leaks? Plain old fixed steel cam gears on this mill, no tumble generator valves. I'm going to try some starter fluid on the intake system today. 1 Link to comment Share on other sites More sharing options...
idosubaru Posted August 23, 2022 Share Posted August 23, 2022 I'd swap another MAFI bet you have easy access to those too? I had a 90's Phase I EJ hesitate sometimes (I don't recall when it hesitated) for a year, was perfectly drivable but annoying, and then trouble starting ocassionally for a month, never had any codes. Then one day it randomly tossed a MAF code, swapped it, and it ran perfectly. Fuel pressure regulator? Fuel injector? Another big anecdotal meaningless experience: I had a 2000-ish forester with slight running issues and no check engine light. I checked the easy/obvious things, had already installed new headgaskets/knock sensor as well and when I swapped the entire intake manifold it fixed it. I kept the intake for awhile and wanted to diagnose and test the few components on it but never did. Link to comment Share on other sites More sharing options...
carfreak85 Posted September 9, 2022 Author Share Posted September 9, 2022 Sprayed down the intake piping while the engine was running to no effect. Did notice the oil pressure sender was wet and was emitting bubbles after I shut it off and was inspecting the intake manifold... Will do some laps this weekend with the SSM2 hooked up. Link to comment Share on other sites More sharing options...
carfreak85 Posted September 19, 2022 Author Share Posted September 19, 2022 The car seems to know when it's hooked up to the SSM and behaves as it should. Stumble persists, but the car seems to need a few extra revolutions to fire off after sitting. Link to comment Share on other sites More sharing options...
carfreak85 Posted February 20, 2023 Author Share Posted February 20, 2023 Hooked up the SSM2 and monitored the Misfire channel during the stumble. Nothing registered while it was happening. Stumbles pretty badly at times at low throttle/low load pulling away from stops. Car will accelerate through the stumble with WOT, but you can still feel periodic hesitation in the acceleration, but not the 'bring-you-to-a-crawl' low-speed stumble. Coil checks out, IAC checks out. Link to comment Share on other sites More sharing options...
el_freddo Posted February 21, 2023 Share Posted February 21, 2023 How old is the fuel pump? And if replaced what quality is it? Cheers Bennie Link to comment Share on other sites More sharing options...
azdave Posted February 21, 2023 Share Posted February 21, 2023 I don't know your engine platform so ignore this if I'm way off base but I had a bad throttle position sensor on my 87 EA82. It caused a similar intermittent stumble just off of idle because it was providing bad position values in part of the range. When the throttle was at rest, an idle switch was on so no problems showed. As soon as the throttle shaft turned just a little, the idle switch turned off and the wiper hit a bad section on the circuit. Once past that bad section of the circuit, it ran fine. The problem was most noticeable when gently accelerating from a full stop. If I jumped on the throttle it was not noticed at all. I have an old analog Simpson 260 meter and when reading the resistance across the TPS and manually turning the throttle shaft, the meter's needle jumped all over the place instead of smoothly sweeping back and forth. Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted February 21, 2023 Share Posted February 21, 2023 try tapping on the MAF - or swap as Ido said above. Even cleaning it might be worth trying. 'dropped' valve giudes can be intermittent. Link to comment Share on other sites More sharing options...
carfreak85 Posted March 6, 2023 Author Share Posted March 6, 2023 On 2/20/2023 at 11:44 PM, el_freddo said: How old is the fuel pump? And if replaced what quality is it? Cheers Bennie Fuel pump is original to the chassis during our ownership (200k miles +/-). ODO shows 257k, but ODO was replaced under warranty prior to our ownership. On 2/21/2023 at 4:34 AM, azdave said: I don't know your engine platform so ignore this if I'm way off base but I had a bad throttle position sensor on my 87 EA82. It caused a similar intermittent stumble just off of idle because it was providing bad position values in part of the range. When the throttle was at rest, an idle switch was on so no problems showed. As soon as the throttle shaft turned just a little, the idle switch turned off and the wiper hit a bad section on the circuit. Once past that bad section of the circuit, it ran fine. The problem was most noticeable when gently accelerating from a full stop. If I jumped on the throttle it was not noticed at all. I have an old analog Simpson 260 meter and when reading the resistance across the TPS and manually turning the throttle shaft, the meter's needle jumped all over the place instead of smoothly sweeping back and forth. We hooked up an SSM2 and were able to trace the TPS plot. Shows 0, shows 100, no wacky movement otherwise. Ran the FSM diagnostic procedure and it passed as well. On 2/21/2023 at 8:01 AM, 1 Lucky Texan said: try tapping on the MAF - or swap as Ido said above. Even cleaning it might be worth trying. 'dropped' valve giudes can be intermittent. MAF has been cleaned a couple times, haven't banged on it yet though. @GeneralDisorder has mentioned dropped valve guides not being an issue on '99 EJ253s, but I could be misremembering that... Link to comment Share on other sites More sharing options...
el_freddo Posted March 7, 2023 Share Posted March 7, 2023 Any TGV setup on this early 253? It could be worth deleting these and see what happens. I mention this as a mate had his GT series 2 Foz do the same thing to the point sometimes it would almost die completely as you tried to cross an intersection. It turned out the TGV system was doing something stupid but not throwing a code. I believe he deleted the butterflies from the inlet manifold and left it as is. This resolved the issue and allowed him to tow his camper trailer around Oz without any further issues. Same thing with WOT - no issue, but partial throttle nothing but issues. Cheers Bennie Link to comment Share on other sites More sharing options...
idosubaru Posted March 7, 2023 Share Posted March 7, 2023 10 hours ago, el_freddo said: Any TGV setup on this early 253? It could be worth deleting these and see what happens. What is TSV? I’ve never heard that term. Googling Subaru TSV didn’t help. Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted March 7, 2023 Share Posted March 7, 2023 tumble generator valve? seems too early but, I dunno when they first got them. Link to comment Share on other sites More sharing options...
el_freddo Posted March 7, 2023 Share Posted March 7, 2023 11 hours ago, idosubaru said: What is TSV? I’ve never heard that term. Googling Subaru TSV didn’t help. TGV - as @1 Lucky Texan said - Tumble generator valve. Its purpose is to better mix the air fuel mixture at idle and maybe low engine revs for better torque (maybe, I’m guessing on this one). If they’re not opening quick enough off the line you’ll have running issues. The reason I mention this is because you’ve got an EJ253 and from what I understand of the later EJ253s they got the TGV setup. Yours could be the market test bed engine to get some real world data before going to full production on all models - who knows. But I reckon it’s worth looking into. PM me your VIN and I’ll see what I can find in the parts diagrams for your engine and get back to you. Cheers Bennie Link to comment Share on other sites More sharing options...
idosubaru Posted March 8, 2023 Share Posted March 8, 2023 3 hours ago, el_freddo said: TGV - as @1 Lucky Texan said - Tumble generator valve. No non turbo US EJ25's had that unless they slapped it on some late EJ25 nonturbo's that snuck past me. I'd guess that's a turbo only part in the US. 99 EJ25 isn't turbo, there are no turbo EJ25's in the 90's in the US. 1 1 Link to comment Share on other sites More sharing options...
idosubaru Posted March 8, 2023 Share Posted March 8, 2023 On 9/9/2022 at 6:09 PM, carfreak85 said: Sprayed down the intake piping while the engine was running to no effect. Did notice the oil pressure sender was wet and was emitting bubbles after I shut it off and was inspecting the intake manifold... Will do some laps this weekend with the SSM2 hooked up. Can you map fuel trims while it drives normal and through one of it's episodes and compare? Link to comment Share on other sites More sharing options...
carfreak85 Posted March 11, 2023 Author Share Posted March 11, 2023 On 3/7/2023 at 3:00 PM, el_freddo said: The reason I mention this is because you’ve got an EJ253 and from what I understand of the later EJ253s they got the TGV setup. Yours could be the market test bed engine to get some real world data before going to full production on all models - who knows. But I reckon it’s worth looking into. No TGVs on this engine or fun camshaft toys like some of the later EJ253s. Never engine swapped either. On 3/7/2023 at 6:50 PM, idosubaru said: Can you map fuel trims while it drives normal and through one of it's episodes and compare? I will look into that today. 1 Link to comment Share on other sites More sharing options...
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