2000 Lesabre Rough idle after cold start

[Frank2814]

My daughter's 2000 Lesabre sputters after cold start when in reverse or drive. It's fine after it heats up. We bought the car 2 years ago and I replaced an aftermarket fuel pump to fix the gas gauge issue. I also went ahead and replaced the fuel filter. That was over a year ago. The past 3 or 4 months this issue popped up. Recently I started throwing parts at the problem. The car is almost 24 years old so I figured it wouldn't hurt to replace them. I replaced the MAF, IAC and the Fuel pressure regulator. I also replaced the shrader valve on the fuel rail. Yesterday, I removed the MAF sensor and sprayed some throttle body cleaner in the Throttle Body. I also cleaned that little sensor attached to the big main air intake hose. Before replacing all that stuff, I sprayed a little bit of Carb Cleaner around areas of the vacuum lines. The engine didn't rev up or down anywhere. I'm going to change the shrader valve again today. Maybe I got a cheapo one and the seals are bad. I'm also going to inspect the hole it comes from. Maybe I left a small amount of broken gasket in there or something. If you can let me know if anyone has had similar issues.

 

[Frank2814]

It's not throwing any codes.

 

[HotZ28]

You are going around in circles & throwing parts @ a problem without proper diagnosis! There is no mention of any codes? The fuel pressure test port valve has nothing to do with the problem you mentioned, unless it is leaking fuel! Do you have a scanner & fuel pressure tester?

 

[Frank2814]

You are going around in circles & throwing parts @ a problem without proper diagnosis! There is no mention of any codes? The fuel pressure test port valve has nothing to do with the problem you mentioned, unless it is leaking fuel! Do you have a scanner & fuel pressure tester?

I mentioned in the post after the main post that it's not giving any codes. I have a cheapo OBD 2 scanner. I'll double check to see if it does fuel pressure. I just remembered that I have a blutooth OBD2. Maybe that will work. If not I'll buy one. It runs fine soon after driving so I'm thinking the fuel pump is giving good pressure. After a few hours I've pushed the shrader valve in and no fuel squirts out like its done in the past. So the system doesn't seem to hold positive pressure when off. This all started a few months ago. I did get a code (I don't remember the number) but the gas cap was loose. After that. I noticed the strange idle. I can't say when exactly it started to behave that way because it's my 18 year old daughter's car and they're kinda mindless at that age. Anyway. Ill pick up a fuel Pressure gauge in the next few days. In the meantime I'll probably just sniff around and try to find it that way. Did I mention that I'm not a mechanic do my diagnosis skills are far from perfect. At least I'm an honest idiot.

 

[HotZ28]

There are no fuel pressure sensor on the fuel rail, or anywhere else that would send OBDII codes to the PCM for low pressure! Forget about that.

 

[ulycyc]

How old are the sparkplugs and ign.wires? Throttle body cleaner is not the best stuff to use on or near the maf. I would buy maf cleaner and re-clean it. Also a lazy O2sensor can cause cold stumbles. A leaking fuel injector can cause the stumble until it burns off what leaked. This is what may cause no pressure when you check at the schrader valve.

 

[Frank2814]

There are no fuel pressure sensor on the fuel rail, or anywhere else that would send OBDII codes to the PCM for low pressure! Forget about that.

Thanks for the heads up on that. I'll get a fuel pressure gauge in the next few days and I'll probably be able to devote more time on it either Thursday or Friday. Currently, it's just a nuisance but I'm concerned that it might lead to something bigger in the future. I'll probably go ahead and open up the access panel in the trunk that leads to the fuel filter to see and smell if there's anything going on there. Could it be possible that the new gas cap that I put on is not sealing well enough to help the system maintain pressure after it's turned off? That would probably throw a code right? IDK I'll investigate futher and give you an update.

 

[ulycyc]

No. That's different pressure. What's in the fuel line has nothing to do with what's in the tank. The gas cap is sealed so the tank releases the vacuum or pressure into the evap system. If the gas cap was bad it would only leak or let fumes into the atmosphere.

 

[Frank2814]

How old are the sparkplugs and ign.wires? Throttle body cleaner is not the best stuff to use on or near the maf. I would buy maf cleaner and re-clean it. Also a lazy O2sensor can cause cold stumbles. A leaking fuel injector can cause the stumble until it burns off what leaked. This is what may cause no pressure when you check at the schrader valve.

Spark plugs and wires are less than a year old. The MAF sensor was removed during the Throttle Body Cleaning. The MAF is brand new. (It's part of the throwing parts at it thing I explained) I was thinking the seals on the fuel injectors but it definitely makes sense that it could be just leaking.

 

[Frank2814]

Thanks for the heads up on that. I'll get a fuel pressure gauge in the next few days and I'll probably be able to devote more time on it either Thursday or Friday. Currently, it's just a nuisance but I'm concerned that it might lead to something bigger in the future. I'll probably go ahead and open up the access panel in the trunk that leads to the fuel filter to see and smell if there's anything going on there. Could it be possible that the new gas cap that I put on is not sealing well enough to help the system maintain pressure after it's turned off? That would probably throw a code right? IDK I'll investigate futher and give you an update.

I meant access that leads to fuel pump but I'll also check the fuel filter.

 

[Frank2814]

Okay so I work 3rd shift and I asked my daughter if I could drive her car into work tonight. I cranked it up every couple hours today and didn't have the rough idle in reverse and forward all day. I also had no problem when I left for work. I live about 65 miles from work. At around 50 mph it chugged a little but went away after I got up to 55 mph. I tried to replicate that a few times but it drove okay. It was low on gas so I stopped to get gas. After getting gas, I cranked it up and it started to stumble in drive idle and reverse idle. It went away after driving. I got to work and my buddy brought in his fuel pressure gauge. I got 0psi when I hooked up the gauge. I got 10 psi with key turned and no start. I got 48 psi with car running. I plan on checking car throughout the night and posting the pressure with the car off to display whatever it's bled down to from the initial start. See attached pics.

 

[Frank2814]

The above startup was at 10:10 p.m.
Immediately after shutdown it read 40 psi with key removed.

5 min. Later it dropped to 34psi.

See attached pics

 

[Frank2814]

At 11:10 p.m. it dropped to 22 psi.
See attached

 

[Frank2814]

12:10 a.m. 17 psi

 

[Frank2814]

1:10 a.m. 14 psi

 

[Frank2814]

2:10 a.m. 14 psi

 

[Frank2814]

4:45 a.m. 11 psi

 

[Frank2814]

Okay, so on the drive home I got it to give me a code. P0302 (CYLINDER 2 MISFIRE DETECTED)

I replaced the plugs and wires a year ago.

So I'll pull off the wire and inspect it.

Remove spark plug and inspect it.

Put borscope in spark plug hole to observe possible leaking fuel injector.

Test or buy a new coil pack if I haven't found anything by this point.

Any other tips?

 

[Frank2814]

You are going around in circles & throwing parts @ a problem without proper diagnosis! There is no mention of any codes? The fuel pressure test port valve has nothing to do with the problem you mentioned, unless it is leaking fuel! Do you have a scanner & fuel pressure tester?

I've done quite a bit of diagnosing since I first posted. Any input would be greatly appreciated.

 

[Frank2814]

How old are the sparkplugs and ign.wires? Throttle body cleaner is not the best stuff to use on or near the maf. I would buy maf cleaner and re-clean it. Also a lazy O2sensor can cause cold stumbles. A leaking fuel injector can cause the stumble until it burns off what leaked. This is what may cause no pressure when you check at the schrader valve.

I've done some more diagnosing since original post. I eventually got a P0302 code. I went ahead and ordered a coul pack, new injector and spark plug. I plan on cleaning the other fuel injectors while I have the fuel rail out.