I've been having this problem with my car for the past month or so. Sometimes at idle, while accelerating and while cruising the car will stumble, backfires, run rough, miss, just basically running like crap. The rpms bounce up and down, at idle the rpms will drop to like 400, recover, idle ok, then do it again. While doing like 70 in the freeway the rpms will suddenly cut out to around 500 then recover. The rpms bounce between 1000 and 2000 rpm.

The ignition module, cap, coil, wires, fuel filter were replaced within a month. Fuel pressure regulator was been rebuilt last week. Plugs and rotor were replaced within a year and a half.

I found 4 leaking injectors. I replaced them and it ran good for a 4 or 5 days. A few hiccups the first couple days, but nothing major. Last couple days it ran good. Then started acting up again.
I figure the other injectors may be bad too, i have extras, so I replace the other four. It runs perfect for a few days, and now its messing up again.

And while cruising, this happened before any of this was going on, if i was cruising on the freeway at 2300rpm, and if i give it a little bit more gas, the rpms drop to 2000, if i let up the rpms return to normal. While accelerating it would bog and the rpms would not go past 1700-2000 easily. If i let off the gas the rpms would stop bogging out. That might be related.

WTF!!!!!!!

TPS? ECM bad? Fuel pump dieing?

It starts. Occasionally after starting it will stumble around, but once i get it moving it would go fine(until now).

I'm out of ideas and I need an answer quick!

Thanks!

 

Well I reset the ECM to clear the codes so I could see what would pop up. Nothing popped up. The engine was already warm.

I drove it around and it seemed ok. Had a small problem after I got off the freeway though. Right after I got off I got stopped at the light. It idled fine. Then after the light changed and I went to turn, it stumbled around. I turned off onto a residential street and it drove fine.

This confuses me even more.

 

You say you have replaced the ignition module?

Most of the time this happens when not enough or no dielectric grease was applied to the bottom of the ignition module....they will get heat soak and start to act up....if you have replaced what you have said I would have the coil and ignition module checked at autozone or yourself.....

 

Yep, I replaced the module myself. I did put a packet of grease that came with the module on it. The coil is an Accel Supercoil, brand new. The module is a cheap off brand. Its whatever the store brand was. I bought it at United Auto Parts. Cost 22 bucks. I had a feeling it could be the cheapo module, but wasnt sure. I didnt have the cash on me to spring for the better one.

How would I test the module and coil? And are you sure Autozone test them?

Though, what still puzzles me is why it worked perfectly fine for a few days after I replaced 4 of the injectors, then messed up.

Thanks for your help. I'll look into getting, testing or swapping out the module.

Thanks,

Matt

 

by fixing injectors and having it work fine then start messing up on you then replacing the rest and having it work fine again .....it sounds to be fuel related to me ....have you changed the fuel filter lately ???

was there any trash in the fuel regulator or injectors when you rebuilt them ??

 

Yep, fuel filter was changed a few weeks ago. I didnt rebuild the injectors though. My old ones were the Multecs. The ones I put in I had pulled from another car. The rails looked clean, no crap in them. I put about 3 bottles of injector cleaner too.

Another thing I remembered/noticed. I can smell gas when it messes up, like its running really rich. Its not there everytime, but usually. Cant tell about any smoke though, my exhaust is all messed up.

Thanks,

Matt

 

For some reason my computer wont let me edit.


I went to go start it cold. It started fine, then it went to cut out, rpms dropped from like 1300-400. It recovered but ran rough. Code 32 set.

I started it again. Idled at 1500 then started to settle down, then it dropped to 600 for a couple seconds, then back up to 1500, then dropped again. Basically it loped from 1500-600, and it stayed steady for a little bit in between. Smelled rich. Did this for about a minute, then dropped to 400-600 rpm and ran rough, and smelled rich.

 

I bet you money that is the problem....

I'm about 99% sure thats your problem now that you mention that.....

I USED to have one.....I got rid of it when I had the same problems occur.....sudden loss of power and misses, backfires, eratic rpm....

Those coils get hot and that effects there performance.....seriously find your stock coil and replace it with that and see if you problem persists......again I HIGHLY recommend you find a stock coil and convert back....
Here is a photo of the conversion bought to make my HEI a seperate coil pack.....

 

Here is another...

 

Lose the Accel coil, Im surprised it didnt just stop working all together like it did once for me and twice for my friend with the same car.

 

Would a parts place have the stock parts? I bought the car with the Accel setup in it already. Bought it about 3 years ago. Ran good till now. I replaced the old accel with a new one and new module when I did the wires and stuff.

Though it makes sense, cause the fuel system should be good, and i do smell gas when it does it, which tells me that the spark is getting to it to light it off.

Thanks,

Matt

 

Parts store should have em.....just buy a stock one for now and sell your new one on EBAY or something....maybe some mustang driver will buy and forget that it won't fit his car.....

lol......I am betting this is the problem though.....at least find an old one that you know works and use it to "test" and see if the problem persists....

 

Thanks, I'll do that as soon as I can. Would you recommend swapping out the cheapo ignition module too, or just leave it?

Thanks again,

Matt

 

1 at a time till you know the culprit.....

 

Swapped in the stock coil. Same results.

I did notice something new though. My cold start injector is wired to a manual switch, so i can trigger it whenever I want. When the engine started to cut out at idle I hit the switch and it revved back up. That would mean it was running lean, correct?

What controls or affects the air/fuel ratio when the engine is cold?

I know the O2 doesnt send a signal till it warm. What about the TPS, CTS, and MAF?

Or should I still look at a spark problem?

Also, Someone else suggested fuel pump, but wouldnt a bad pump cause problems constantly, not intermittantly like it was, and wouldnt it also cause hard starting and bad pressure at idle?

Also, could a bad check valve in the pump cause the pressure in the system to fall when the engine is off? I have that problem too, and i rebuilt the fuel pressure regulator and it still does it. Though if I pinch the return line it stops falling and occasionally raises a bit, when I let go it continues to fall.

Could a bad check valve mean the pump is bad?

I'm lost on what to do next.

Thanks,

Matt

 

I got bets on a MAF! But dont just go and replace parts until you get it right, unless you cant test that part and you're about 80% sure that is the culprit.

I'd do some more tests, go out and install a mechanical fuel pressure gauge and get the readings while the car is "in the act".

Also, someone who had similar problems to this recently just took his car in to a mechanic to get it fixed he was so frusterated with it. It ended up being catalytic converter being dang near clogged.

Food for thought

 

Wow...time out! Boy, looks like your jumping from one thing to another here guys? IMO, he needs to stop, start at the beginning and test and set things first. Check and set fuel pressure with a gauge. Nose around and check vacuum lines for leaks, cracks,etc. Make sure all your sensors are clean and connected. All other electrical connections clean and tight to include all grounds. Check and set TPS. Start up car and let it warm up to temp then complete the following. Check and set timing with EST connector off. Set IAC, along with idle speed. Recheck timing. Disconnect your neg batt post for 5 minutes to reset ECM and go for a moderate 15min test drive so the ECM can relearn itself, no WOT. Now where are we at, report back your finding?? Fuel pressure PSI with/without vacuum and does it hold. TPS dc reading, Idle Rpms, base timing setting. The over all performance of car during test drive. Then we might be able to point you in the right direction. Your problem can be fuel or ignition, ECM, sensors at this point, we need facts.
Or we can help you **** away your money buying parts one at a time until we all retire and or you go broke.

 

I checked the TPS voltage. Was at .72 at idle. I changed it to .52 and started it. started and idled ok. I then checked to see what it was at WOT. It was only at 4.31V. I adjusted it so it would get to 4.9v at WOT, but at idle it was at 1.14V. I decided to set it back to .50 at idle then go drive around. It drove, but it lacked power, felt like it was bogged the entire time. I came back home and checked it again. It was at 1.16V. I tried putting to .50 and even with the sensor as far as it could go it only got to .71V. Then i turned the key off and on and the voltage dropped to .33V.

It seems that the sensor cant keep the voltage constant or something.

I also checked the ohms on the injectors. All were 17.2 +- .4ohms.

Fuel pressure is at 37lbs at idle, 43lbs when the vacuum line is off. Pressure does not hold when the engine is off. The fuel pressure regulator has been rebuilt in the past 2 weeks. If I pinch the return hose it holds. If I let go it drops. No noticible gas leaks.

With ignition on and engine off, what voltage is the MAF wires put out? Is there even a way to check it?

The engine to firewall ground on the passenger side was reattached at the EGR solinoid bolt. It was unhooked since I bought the car. I felt around the back of the heads and could feel wires comeing from 1 bolt on each of the heads, my guess is those are grounds.

Matt

 

Ok Matt
The problems in your first post are symtoms I experienced with my TPS/IAC and idle not set right. And yes, it took me several times to get it right. I found that setting the TPS at .54vdc at idle was the best overall setting for my motor. WOT was 4plus vdc. Set TPS for .54vdc at idle, then tighten it down, check vdc again at idle to make sure it didn't change. Open the throttle body to WOT, the voltage should go above 4vdc. If that happens, your golden, if it does not, the TPS has an issue. You never told us where the timing is? When you say idles OK, what RPM? Set the timing between 0-6* with EST connector off, I set to 6* then retard it until motor stumbles then I put a degree or two of advance back in, tighten your hold down, check the setting with your timing light. My car will not idle at the book spec for anything, I am set for around 750 RPM, anything lower and it stuggles when in gear idleing. Try that out, let us know. Your fuel pressure seems reasonable with/without vac. So, take the car for a spin, remember the ECM is going to be learning the new setting and adjusting itself so give it some time to regroup before you hammer it. Let us know.

 

TPS voltage doesnt seem to want to stick. I'll set it at .52V, tighten it, check again and its still .52. Then when I start it and check again its up to .65v, then when I shut it off its down to .47v.
Am I not tighting enough or something?

It idled high, I got it down to about 800 or so. It changes occasionally though.

I dont know about the timing. I dont know how to do timeing. Its something I never learned or taught myself. Never seen it done either.

I also put it into field service mode. It never seemed to go into closed loop. Even with the engine warm, and on a hot start.

Thanks,

Matt

 

I put a new PCV valve and new TPS sensor in. I set voltage at idle at .52v.

I started the car, it ran, I checked the voltage again at while it was running. The idle was loping. Whenever the rpms went up the volts from the TPS went up. When the rpms dropped the TPS voltage also dropped. I shut it off. Checked voltage again. It was at .58v. I started it back up, it idled fine. I drove it around the block. It drove, no backfires or stumbling or erratic rpms. Still felt a little bit bogged. The exhaust system is all rusted and busted though, and I could hear that the exhaust note sounded more droning on acceleration.

My dad said its a possibility that the car not running good combined with the exaust being messed up could have plugged the cat. And being that the exhaust is messed up, that itself would cause a power loss, right?

 

Its still not running and I cant afford to not have the car. I dont have time to try to figure out whats wrong. Its goin to the shop in a couple days.

If anyone thinks of anything beforehand please let me know.

Thanks for the help though.

Matt

 

replace yer cat already lol. If you know it's on it's way out anyways, it's better to just take it to MIDAS or where-ever, pay 150 or so for a new cat and them to install it, instead of 80 dollars for some guy to diagnose it being the cat (and a bunch of other problems that do not directly relate albeit), plus the other 150 to install the cat, so you're looking at a whole bunch more money and it all depends on what ELSE they find wrong with the car.

Shops dont have a problem telling you what is wrong with the car, that's how they get money hehe.

 

The entire exhaust from the cat back is going to be replaced first. It needs it done badly. And it my parents gift to me, so I dont have to pay for it. Once that is done I will probably look at more. Right now I can even stick my head in the engine compartment cause the exhaust fumes burns my eyes.