LB2739

05 manual with 105,000 miles
mods
Cat delete and catback. Don't remember the brand its been years.
BHR new style ignition coils and wires
everything else is stock.

My problem is very odd. On my way to work when I get off the highway and stop at the stop light at the end of the off ramp. My rpm will drop so low it almost stalls for just a sec then its fine the entire time I wait for the light to change. Well this morning it did stall but started right back up no problem. I have had this issue even before the few mods I have done. It never does it at any other stop. Full tank low tank doesn't change. Only does it the instant the car stops.
I take the car out of gear and coast down the ramp a good 15 seconds idles fine all the way down but then right when the car stops its drops. Iv tried giving it a couple good reves on the coast down and still does it.
I have just ignored it till now since it never stalled and it only ever does it at that one stop. I daily drive this car.

Spark plugs are fresh. Oil is new and full. No codes other than the no cat that pops up once every 3 months or so that I verify and clear. No hot start issues.
Everyone I have asked has been stumped to what could be the issue. Especially since its a manual and it only does it at that stop.

sonicsdaman

iTrader: (3)

TL:DR

fuel pump or engine compression

0-TO-100_Real_Quick

Do you have the ability to see fuel trims and/or MAF readings?

LB2739

Answers like this are why I almost didn't even post. If it was 1 of the 2 why only at the one stop? Why not every time I stop?

I keep forgetting to have my scanner running when I go to work. Since that's the only time it ever does this I only get one shot a work day. Ill try to remember tomorrow.

Loki

iTrader: (1)

The fact that it happens at only one stop is not the important part. The fact that it happens at all is the issue, and so before we noodle on what makes that stop special lets get a bit more info. Get the fuel trim and airflow measurements on a warm stationary idle.

You're coming off a highway run so it's possible the fuel pump heats up. When stopped the fuel pump runs in a lower mode. So it's possible that while you coast its still in high speed mode (and you're not consuming fuel anyway), but once you come to a stop and it goes into low mode, it's no longer providing enough fuel pressure.
This is the only thing that makes sense to me so far.

See if you recreate the issue on another offramp, maybe just take the next exit and see what happens.

Have you actually had compression tested? What about ignition coil age?

sonicsdaman

iTrader: (3)

If it's a failing or clogged fuel pump it will get warmer with continued/struggling use, which would affect it after getting off the highway...
Also you give very little about the car and the previous maintenance of it. You're at 105k miles, are you on the original engine still? original fuel pump? do you premix? how old is the battery? tighten down the terminals lately?

All that being said you need to get a data log of everything. It's hard enough to diagnose a car let alone through the interwebz

0-TO-100_Real_Quick

Yeah, it almost sounds like an issue I ran into recently where the fuel trims were out of wack due to a vacuum leak. When I reset the trims working on the car one night, the engine had a hard time keeping idle at a stop. It would only do it at a stop though. I noticed the MAF g/s reading would stay higher at a slow speed in neutral, and then when I came to a stop, the idle fuel map would activate and the engine RPM would flutter, occasionally stall, until the fuel trims compensated. But during those few seconds right after a full stop, the idle was rough. I could watch my fuel trim go to zero at first stop, and then climb up to anywhere from 8-12.

When was the last time you looked at your intake air filter or cleaned your MAF? Also, have you tried replicating this issue, say like going for a drive down a highway for 20 minutes and then coming to a stop? As Sonic mentioned, it very well could be the fuel pump as well. I think the fuel pump has an active recall, so you could go get that checked out if you haven't already.

Tamas

iTrader: (1)

The recall was for the "fuel pump filter kit", whatever exactly that means. Not sure if the entire fuel pump would be replaced... or would it?

LB2739

I think its very important as it ONLY happens at that off ramp. I obviously drive the highway back home from work and it doesn't happen. No compression tests done since I haven't had the need to do it. I said before I have the NEW BHR coil packs and they came out this year.

since you TL:DR what little I gave already why would you ask for more into not to read? I said all the mods done so you could easily assume nothing else has changed. original engine and pump. No premix. Battery is less than a year old. terminals are good and again this has been an issue for years. Oil changed every 3k miles even by original owner. I have all the documents.

Intake filter was replaced 3 months ago. I can only get it to do it at that one stop on the way into work. wont do it coming home or any other time getting off the highway. I cleaned the MAF when I did the air filter.

I can tell you all now any regular maintenance has been done and always done before needed. I don't wait for tires to reach the wear marks before replacing them.

I want to say again this has been going on for years but today it actually stalled that's why I'm asking for help. I will try to get the fuel trim and airflow measurements from warmed up idle and when it acts up at that light tomorrow.

LB2739

fuel pump sealing rings that's all I see under fuel related recalls.

Loki

iTrader: (1)

Correct, the pump is not usually replaced. Only the ring and seal, as well as fuel tank insulation for some model years.

The questions might be frustrating, but I hope you don't expect us to figure this out immediately from the internet when people who can touch the car haven't been able to crack it. So let's not go down the road of criticizing the replies you get -- it will ensure you get fewer replies.


Do all offramps in your area end in a stop or is that the only one? Around here there are very few offramps with stops or lights due to obvious accident risk.


Also where are you and what's the external temperature like? Are you running AC?

LB2739

I'm fine with questions. It helps me check things I haven't thought of or know how to. I'm not expecting anyone to solve this problem immediately. I haven't rushed anyone to help. I dont even expect anyone to figure it out since its such an odd problem. I have had this issue for years minus the stall yesterday. I have every right to criticise a TL:DR reply. Its not helping anything but a person's post count. If people don't want to help that is fine. Being a member does not mean you have to help anyone but if the best you can come up with is TL:DR I can deal with fewer. Next time you ask a question imagine getting that as a reply and how much it helped you.

Obviously not all have stops but even the ones that do I cant get it to happen.

I have filled my location info out on my profile. USA Iowa. It is cold now but this happens even in the summer.
I got a SS of some readings today. It didn't stall and the rpm only dropped a tad this time.
top left is the short term fuel trim.

LB2739

This was at idle but with it being cold out today the engine temp was only 175ish.

sonicsdaman

iTrader: (3)

You posted in the newbie section, expect to get some hazing. The car/platform is 15+ years old and your "problem" is not unique.
Just because I posted TL:DR doesn't mean I did not in fact read it.

I'm not paid to spoon feed you answers.

Generating Power at Full Throttle
• Ignition Coils
• Spark Plugs
• Spark Plug Wires
• Engine Compression
• E-Shaft Sensor (ESS)
• Air Filter
• Intake Valving
• Throttle Body
• Mass Air Flow Sensor (MAF)
• Fuel Pump
• Fuel Injectors
• Catalytic Converter (Cat)

Keeping the Engine at a Cruise
• Ignition Coils
• Spark Plugs
• Spark Plug Wires
• Engine Compression
• E-Shaft Sensor (ESS)
• Intake Valving
• Throttle Body
• Mass Air Flow Sensor (MAF)
• Fuel Pump
• Fuel Injectors
• Front O2 sensor
• Catalytic Converter (Cat)


Keeping the Engine at an Idle
• Ignition Coils
• Spark Plugs
• Spark Plug Wires
• Engine Compression
• E-Shaft Sensor (ESS)
• Mass Air Flow Sensor (MAF)
• Front O2 sensor
• Catalytic Converter (Cat)
• Intake Vaccum



want a hint? your LTFT is wrong (now that we have a data log we can point you in a better direction)

0-TO-100_Real_Quick

I'm no expert in engine tuning, but if the AFR's went lean and the STFT spiked to compensate, that tells me there's either a vacuum leak or an issue with fuel delivery. Your fuel consumption rate does drop right at that time too. If it was me, over the next week, I'd monitor those and see if it repeats just like that. If it does, you might have a fuel delivery issue.

Does your scanner show intake air flow rates? If it does, I think we can eliminate the vacuum leak possibility if you show healthy numbers at idle and at your traffic light stop. But that's just my opinion, others may have some deeper knowledge that I haven't factored in.

EDIT: if you reset your fuel trims, what happens?

sonicsdaman

iTrader: (3)

OP needs to give us more than just an idle snap shot

Fuel trim should be checked at idle, at 1,500 rpm and at 2,500 rpm. In addition to these no-load checks, drive the vehicle at various steady load conditions and watch for fuel trim variation. If long-term fuel trim (LTFT) for bank 1 is 25% at idle, but corrects to 4% at 1,500 and 2,500 rpm, focus on factors that cause a lean condition at idle, such as a vacuum leak. If the condition exists in all rpm ranges, the cause is more likely a fuel supply issue caused by low fuel pressure, a restricted injector or a defective sensor input from a MAF or engine temperature sensor.

Loki

iTrader: (1)

So in the pictures posted, LTFT is at 15. That's not OK, you have a vacuum leak. Under some conditions, like that stop sign, the leak may open larger than fuel trim can compensate and it stalls out.

Look for cracked or disconnected hoses anywhere after the MAF.

LB2739

I didn't ask to be spoon fed. You clearly didn't read where I said I don't expect people to help. If you feel like I'm telling you to help me that's on you and you can stop now.

Ill reset them tonight and see monday if it changes anything and ill check if the ap shows flow rates and get a snapshot up.
If people want more info they have to tell me what they want. I gave what was asked for. No one said I needed to give them 1500 2500 rpm or under load logs. I was just asked to get info for idle warmed up and when it happens. Ill check for vacuum leaks this weekend and do the suggested tests.

I will check this weekend.