I've recently had some idling issues with my GTA. It has gotten better with slightly reduced fuel pressure (38 PSI on the nose) but it still fluctuates in park and neutral. The best guess was my park/neutral switch but since it's liveable I have left it alone for now. Otherwise she ran great.

Thursday evening I filled up my tank from the half way mark. Dropped a buddy off and went home. The next morning I picked up my buddy again and got on the freeway. Just as we got on it started bucking (like it was severely missing) and wouldn't rev at all. She stalled by the time I made it to the shoulder. She fired right back up and felt fine for a minute, but stalled again at least twice on the way back home to get my ZJ.

After work I stuck my fuel pressure gauge on and it took a few tries to get it to idle. It would run for maybe ten seconds then sputter out. Five or six tries and she fired and idled decently, aside from that slight fluctuation. Even while sputtering and dying the fuel pressure acted just like I'd expect, it didn't do anything funny at all and definitely didn't drop out while it was sputtering. My very first thought was the fuel pump but now I have my doubts. No codes thrown at all, no CES light until the engine died (of course).

Is it feasible at all that I just got a REALLY bad *half* tank of gas? Bad enough to pollute the half tank I already had enough to cause this? Any suggestions before I drain a good sixty litres of gas into jerry cans?

Filters, plugs, leads, cap and rotor have all been in for a few years at least but there's less than 10k on 'em. I'll pull an easy plug and see what it looks like but the only thing done prior was filling the gas tank. Coincidence?

 

this happend to me on my way to back to college last year, it was becuase of my spark plugs, the engine was runing lean and destroyed the plugs!

 

I pulled the #1 plug and it looks great. No abnormal wear or deposits, and the gap (visually) looks fine. Just for the hell of it I richened my AFPR a little and it's still misbehaving. Even while cold it will start fairly quickly, after say two seconds of cranking. It idles for a few seconds before it sputters out and dies, even if I goose the throttle. It'll keep running after five or six tries, although it will eventually die out. The fuel pressure doesn't drop below 30 psi the entire time with the vacuum line hooked up or 40 with it disconnected. Still no CES light, no codes.

Short of buying a bunch of jerrycans I'm not sure what else to do.

 

I have seen threads that indicate 38 PSI with the vacuum hose connected and 45 PSI with the vacuum hose removed is rather 'standard' PSI readings for a healthy fuel pump, regulator, injectors and fuel line 'system'.

I would think that your fuel pressure would reach about 38 PSI and stabilize. The fuel pump should have a one way valve that should be maintaining the fuel pressure and only when the engine is shut off should it ever so slowly allow that pressure to bleed down over maybe 15 or 30 minutes. To see a reading of 30 PSI would seem to me be an indication that something is not 'normal'.

However, why would this be an issue after adding a half tank full of new gas ... that is a puzzle. I suppose just to eliminate the 'bad fuel' theory it would be of interest to drain that tank, introduce about 5 gallons of new gas from a different gas station, run the suspect fuel out of the fuel lines and injectors and see if there is any improvement. It would be nice to completely RULE OUT the quality of gas from being an issue. If you have no further problem then it would appear to be a 'bad gas' issue. If you continue to have the same problem then it would appear to NOT be a 'bad gas' issue. Then you can concentrate on other theories. It is kind of hard to believe that you happened to get bad gas but you just never know.

Then if it were me I think I would really pay particular attention to that fuel pressure.

I would also suggest you check every single vacuum hose for breaks or cracks in every inch of the hoses, especially where they contact the fittings. If you can rule out a vacuum leak via a hose that would give you confidence that this is not the (or a) source of your problems.

I wish you could determine if your engine was stopping due to excess fuel or not enough fuel. If it is excess fuel maybe your coolant temperature sensor that feeds information back to the ECM is constantly indicating that the engine is COLD (meaning that the sensor has consistently high resistance of 5 or 10 thousand ohms and never drops down near 200 ohms). If the ECM is told the engine is COLD then more fuel will be introduced even if the engine is actually warmed up.

I would say your 2 seconds starting time would be considered 'just right' so it is interesting that you have problems right after that.

Make sure the valve that opens inside the horn of the air intake is also behaving and is not stuck closed and does indeed change when vacuum to that valve is changed as the engine warms up. Lack of a sufficient volume of air would look like a rich mixture. Being closed would allow a cold start but not opening when the engine has warmed would be a problem.

 

At the moment I have it set to 40 psi with the vacuum line disconnected, and it drops to around 30 with it hooked up and running. Last time I read into it a 10 psi drop at idle between the vacuum line disconnected and then hooked up was perfectly normal. It increases up to 40 as the throttle is opened. Have I been misinformed? The normal pressure range for a stock TPI system is in the 38-45 PSI range, that might be where you're getting your numbers.

The engine is misbehaving even when stone cold now so that pretty much rules out the temp sensor.

You've lost me with the 'air horn' suggestion. TPI engines don't have any vacuum actuated valves in the intake tract. TBI engines do, but not an LB9.

I'm wondering... I'm still running an Accel ignition module that I got with the distributor about five years ago. I've read that Accel modules tend to be flakey and can cause all sorts of weird running problems. Tomorrow evening I'll swap in my old OE module out of the old distributor (amazingly, still in my parts bin) just to rule it out.

 

So I swapped in my old ignition module just to rule that out. It seemed to idle better, although it did still die on me one time seconds after starting. Hoping for the best, I took it for a spin around the block. I made it to the corner, went to give it a little gas, and it bogged down and almost stalled. It felt WAY worse than a single cylinder misfire. So I broghter 'er back home, barely touching the gas along the way.

It revs okay in neutral, doesn't idle too well, chuggs and stalls occasionally especially right after starting, and wants to die under any load once I touch the gas. I also cleaned the IAC motor (again) for the idling issue but it was still damned near spotless from when I did the intake gaskets last year. Fuel pressure looks fine in park and the one plug I inspected looks great. I couldn't see any arcing on the leads at all when I fired it up in pitch darkness this morning before work. The cap and rotor are nice and clean, little to no wear.

Could a flakey park/neutral switch be screwing with my ECM this badly? Or am I back to the bad gas idea? The gas station tells me that they've had no other complaints, not that they'd tell me if they had. What else should I be looking at?

 

Just 'cause it's easy I tried swapping in an old coil and a MAP sensor that I had lying around from my old 4.3L Jimmy (same part numbers). No change at all, still stalling. I think the exhaust smells really weird too, I want to say it's sulphur-ish but that's just a guess and might not even be from the exhaust.

Any suggestions guys? It's hard to get excited over my new Hawks seat upholstery kit when I can't even take the damned thing out for a ride.

 

Any suggestions at all? I really should have put a better title on this one.

Following my FSM, I pulled a spark plug lead one at a time while running to see if I have a dead cylinder. Nothing, each one dropped the revs about 50-100 rpm, every cylinder behaving the same way. Even with the insulated pliers I still got two pretty decent zapps. lol

What's left? Pick-up coil, ECM, or my bad gas theory? I'd hate to have all of those gas cans lying around when all is said and done if I don't have to, so it's pretty much a last resort.

 

I had my doubts but you might be on to something here. I unplugged the temp sensor for the ECM and it fired up to a nice steady idle. CES light was on of course, but it idles smoothly. Shutting down and plugging it back in and it's back to stuttering for a few seconds and dying out. Unplug it again and it fires right up and idles. I assume the ECM is in some sort of limp mode but it's progress. Once the weather clears up I'll take it for a quick spin with it disconnected, just to see if the driveability problems have gotten better.

After work I picked up a new temp sensor. Without installing it in the intake I plugged it in (I figure it and a cold engine are the same temp for a few seconds anyway). Again it starts, stutters, and dies even with the new sensor. So... guys... what do I do with this thing? lol

 

Wow that really sucks. You might just have to replace the whole ecm but I don't have much experience with the fuel injection.

 

Sblackfoot,
seems like I kind of got the same problem as you. Read below. I can keep the car running somewhat if I constantly pump the gas pedal. I too notice a smell after a few minutes like really hot metal smell. Maybe it's the damn converter stopped up. I'm stumped. One more tidbit. It was running great until I stopped to get a few gallons of gas. After I got about 3 miles down the road is when my problems started. Don't know if that's is just a coinsidense or not. Of course the gas station say's they had no other complaints.



car runs for about 2 seconds then dies. I unplugged the coolant or temp sensor located next to the thermostat on top front of the motor and it ran fine but at a real high idle. thought sure that was my problem. installed a new sensor, plugged it back end but car only ran for a couple seconds. I unplugged the sensor and car ran fine again but real high idle. I decided since the car was running now I could take it to the shop. I started it once more with the sensor disconnected to see how long it would run before I got out on the road. It did run for 3 minutes or so at high idle but then died and now with the sensor plugged or unplugged it will just run for a few seconds. The battery was bad and I replaced it but still the same problem. I also changed the fuel filter. It the fuel pump is bad I would not think it would have run for the 3 or 4 minutes or so. Need help, would like to take it to Cruising the Coast next week.

 

A few more things:

I went out to experiment. TPS looks good, voltages in range and smooth on my analog VM. With the MAP disconnected it behaves just like the CTS is unplugged, it idles with a CES light. With the TPS disconnected it idles high (1500 rpm or so), again with a CES light. Everything hooked up, stumbles and dies without a CES light.

While I had my DVM out I checked my injectors. ALL over the place, with a pair at around 17 ohms and the rest ranging down as low as 8 ohms. Okay new injectors on the shopping list, but I can't see that causing my issues... can it?

Another strange thing I noticed: For whatever reason my headlights now pop up but stay off when I hit the running lights. This is new. Coincidence, related, or haunted?

 

Fuel injectors like that will definitely cause your idling issues. As far as the headlights, I'd say haunted.

 

sBlackfoot
I have the same thing going on with my stock 89 camaro. It has been setting up for a four are five months it was running fine when I parked it. The battery was bad when I parked it. Put a new battery in today and all this started. I am idling a little higher when i unplug the temp senser more like 2k. Have you found out anything sence your last post?

 

I've had the same problems, almost to a T.
I've dropped close to a grand into parts this past month, fixing stuff that needed to be fixed anyway. From my coil to my TBI to my timing chain. Nothing stopped the bogging/bucking. Exhaust smells real rich for me, though, but that's a whole other issue in itself.
Now I've reached a hypothesis that I'm gonna check out tomorrow. Restricted catalytic converter is my last idea. I've replaced dang near everything else. Neutral Safety Switch hasn't been ruled out, has it?

 

I though of that too. but mine chranks up fine and then dies about 2seconds later. And fuel is still going into the TB. I can sit there and work the gas and keep it running for as long as you can stand to wast the gas. Not as easy in gear (auto trans).

 

I don't have a wiring diagram here to look at..... But, if I remember right the neutral/park switch is only a factor in the starting circuit. I don't think that it is in the loop with the key in the run position.

I would revisit your injectors. Look up what the resistance spec should be. I think the range is from 10 - 15 ohms. Sounds like you have at least one that has too much resistance and one that has not enough. I had an injector go bad on me once and it caused all kinds of problems including causing the ECM to throw incorrect codes. Check them with a noid light. What I saw was a difference in the strength of pulse on one side of the engine. It was pulsing, but with different intensity.

Also check the voltage at both your MAP and CTS. If I remember correctly the voltage from the ECM should be 5V with the sensors unplugged. Also check the voltage going to the injectors. With the key on you should have 5V (I think) going to them. Double check your ground at the ECM. Also voltage to the ECM.

I would pull all of your plugs out and inspect them. You can tell a lot from what the plugs tell you.

 

I've been going threw something like this a car I got from the junk yard and did drain and refill tank I think I'm looking at a fuel press regulator prob. just a thought let you know if it works.

 

Sorry guys, I didn't realize that anyone had replied to this thread.

Since I last posted I got fed up and put it away for the winter. My plan of attack, hopefully soon, is to replace the injectors. With the way that they're ohm'ing out, they need to get replaced anyway. I picked up a set of Ford injectors in a junk yard that appear to work, I think I can make 'em fit. If I hadn't been deathly ill with a chest infection AND a brutal cold for the past three weeks I'd have 'em in by now.

The more I think about it, I really don't buy the NSS theory. Sure there are several sets of wires coming out of it. It locks out the starter but it also controls the reverse lights, THAT explains the extra leads. My FSM doesn't show it doing anything else. It cranks in park and in neutral, not in gear, and the lights work. The NSS is fine.

It seems weird that an injector or two would suddenly cause issues like this but them ol' Multecs have been known to be troublesome, and they ARE pushing twenty years old...

 

Quick update. In the fall I grabbed a set of injectors out of a Crown Vic. The yellow Bosch-type ones, offhand I cannot remember what the flow is but it seemed reasonable at the time. They were a little too short to just drop in so I made some spacers at work to shim them up .050". Last night I tore the Multecs out and tonight I installed the junkyard Fords.

Amazingly, no leaks even with my oddball spacer setup. It took a few seconds of cranking to get it to fire (injectors were full of air and a little oil), but it fired up and settled into a nice idle. No stalling! The idle still fluctuates a little bit (75 rpm or so) but WAY better than it was. So far so good... Unfortunately the test drive will have to wait until the spring. With any luck she'll be good to go but I'm not holding my breath.

 

To update an old thread, I just drove the car around the block for the first time since it had it's brutal stalling issues last fall and for the first time with the Crown Vic injectors. The ol' girl ran great! No stalling or hesitation, no smoke, no codes, nothing! I'd call my makeshift Crown Vic injectors a success.

The only minor issue is the idle still fluctuates 100 rpm or so in park or neutral. In gear it seems stable and like I said, so far she's running great. Just that idle...

 

I came upon this thread when researching my recent problems. I thought I had an ignition problem, but it was an injector. One was getting hot and shorting out, that was enough for the ECM to shut them all down. Runs great now with some Bosch type IIIs from FIC. Best $200 I ever spent on the car.