Hmmm. My engine doesn't like go above 3300RPMS. After that the car loses power and starts slowing down?

[jockhater2]

I have to shift @ 3300 or before. Otherwise it starts slowing down.

The problem just recently started happening.

Car has
Resurfaced head
new timing belt/sprocket
new radiator
new water pump
new injectors
new fuel pump regulator (last year)
New fuel filter (last year)
new MAF sensor (did that today and it fixed the rough idle and hesitation)
new rotor/distributor cap (it is held on by zip ties. maybe its out of alignment?)


Fuel pump works great
Today since the new MAF sensor the car is now running/idleing like a champ finally.
Idle is at/around correct RPMS
No fuel leaks
Smoke tested the crap out of the car. No vacuum leaks.

I am going to test the O2 sensor tomorrow. Its about 7 years old.

I only run supreme gas and mobile 1 high mileage oil or royal purple


This is a bad problem because it's not in the bentley

[ps2375]

Have you checked the cat?

[jockhater2]

Have you checked the cat?

Ohhh. As in. Is it clogged?
I had a new one installed 3 years ago.

How would I check if it is clogged?

[ziddey]

You can usually tell an exhaust problem just at the tailpipe. You should have an idea what normal is.

How sure are you of your fuel pumps working? I know your FPR is relatively new, but have you checked pressure?

Have you checked the ignition timing? Zip ties!? Check that it is advancing properly at higher RPMs. That'd be a pretty big problem.

Coolant temperature sensor? Know that the car is going into closed loop?

Does it rev freely above 3300rpm in neutral? Any stuttering?

No misfires?

Has it had this problem before you swapped in the new AFM? AFAIK, the mixture adjustment is part of the AFM, although the ECU will quickly learn and adapt, assuming the o2 sensor is working properly.

Go through the procedure to reset the ECU.

With the car warm and fan cycled, unplug the CTS and rev to 3k 3-4 times. At this point, you might as well check your ignition timing @ 2500rpm as well. Plug the sensor back in.

A reset may fix it temporarily as it is.


Also, make sure your idle switch is working properly. You should be able to hear it click when pulling the throttle off idle, and click when returning. You can easily check it electrically as well. It's just a switch after all.

[jockhater2]

You can usually tell an exhaust problem just at the tailpipe. You should have an idea what normal is.

How sure are you of your fuel pumps working? I know your FPR is relatively new, but have you checked pressure?

Have you checked the ignition timing? Zip ties!? Check that it is advancing properly at higher RPMs. That'd be a pretty big problem.

Coolant temperature sensor? Know that the car is going into closed loop?

Does it rev freely above 3300rpm in neutral? Any stuttering?

No misfires?

Has it had this problem before you swapped in the new AFM? AFAIK, the mixture adjustment is part of the AFM, although the ECU will quickly learn and adapt, assuming the o2 sensor is working properly.

Go through the procedure to reset the ECU.

With the car warm and fan cycled, unplug the CTS and rev to 3k 3-4 times. At this point, you might as well check your ignition timing @ 2500rpm as well. Plug the sensor back in.

A reset may fix it temporarily as it is.


Also, make sure your idle switch is working properly. You should be able to hear it click when pulling the throttle off idle, and click when returning. You can easily check it electrically as well. It's just a switch after all.

Exhaust is fine.
fuel pump works. Tested it several times.
Ignition timing is correct. Yeah. Zip ties. The spring clamps broke before I owned the car.
Coolant temp sensor is new. Put it in back in february or march
Yes. It revs freely in neutral. and nope. No stuttering.

no misfires.
We still need to test the 02 sensory
I will try reseting the ecu.
Idle switch is working.


We think its the fuel lines. I had a leak in the fuel line that goes into the common rail. And we used some fuel line we had in the garage. We thing its the wrong size. I am going to check that when I see the car next. My brother is always borrowing it.

[jockhater2]

figured out the problem. Wrong fuel line size

[tmerritt]

i'm having this problem with my 92 digi1 8v. it was fine a week ago then i replaced my clutch. after getting everything put back together i go to drive and have exact symptoms as above. i've recently replaced the distributor cap, rotor, plugs, wires, both coolant sensors, and switched out my maf. i'm gonna try unhooking the o2 in the morning because other threads have hinted to that helping. but i'm at a halt as to what to do.

[jockhater2]

i'm having this problem with my 92 digi1 8v. it was fine a week ago then i replaced my clutch. after getting everything put back together i go to drive and have exact symptoms as above. i've recently replaced the distributor cap, rotor, plugs, wires, both coolant sensors, and switched out my maf. i'm gonna try unhooking the o2 in the morning because other threads have hinted to that helping. but i'm at a halt as to what to do.

my problem was because we used the wrong fuel lines size when we fixed the leak.

And replacing my MAF sensor helped my rough idle

[tmerritt]

i haven't replaced any fuel lines so could it be my pump on the way out?

[jockhater2]

i haven't replaced any fuel lines so could it be my pump on the way out?

I'm sorry. I am not much help. I am 22 and do all the work on the car thanks to the bentley. I don't know a whole lot.

[tmerritt]

I'm in the same boat. I'm learning as I go but i don't wanna fork out the money for parts I'm not sure I even need. I'm living the broke college student life.

[jockhater2]

I'm in the same boat. I'm learning as I go but i don't wanna fork out the money for parts I'm not sure I even need. I'm living the broke college student life.

Do you have a bentley manual? because honestly. Everything you need to know to fix these cars is described in that manual.
That's how I figured out my MAF sensor was bad. Because I went through the symptoms in the manual.
That's how I figured out my Fuel Pressure Regulator was bad last year. And my Idle Air Stabilizer.

Now my car is misfiring but that one was easy. Bad wires. There arcing out at the cap.

[tmerritt]

i've been reading it on pdf and googling alot of my problems. i guess a paper copy would be better but i'll look over it again and see if it helps.

[jockhater2]

i've been reading it on pdf and googling alot of my problems. i guess a paper copy would be better but i'll look over it again and see if it helps.

You can order it at www.germanautoparts.com I believe. Before my dad died he owned an ran a european auto repair shop. thats how I got my manual plus a garage full of spare parts. Most the parts the car has needed. I found in the 3rd garage. I am very lucky and happy that he salvaged parts.

Yeah. The bentley manual is God's gift to this green earth. It helps way more than asking someone. trust me.
Just look up fuel symptoms and keep checking for what it could be that can cause a symptom of a loss of power.

[jockhater2]

i've been reading it on pdf and googling alot of my problems. i guess a paper copy would be better but i'll look over it again and see if it helps.

Hey. How is your car going? Is it getting any better.

Here are some more things I found out about my car.

Ok. So when I overheated my engine and had to do the head gasket.
I didn't read in the Bentley that the hydraulic lifter caps have to go back in the exact place they came out of. So I just bought new ones and the car has gained a lot of power back.
It was misfiring also. My spark plug wires were corroded and fouled.
SO that helped.
Now the spark plug on cylinder is getting spark but when I pull it the idle doesn't get rough. And the spark plug is carbon fouled. So I am going to replace the spark plugs to.