Hi everyone,

I'm Max 92 SE 120,000 km (Noob, though...:-)
I've been looking thru the postings here and found quite a few descriptions similar to the problem I got.

This is how it feels like:

"It felt like either a terrible ignition miss or no fuel. I also noticed that when I slowed down, there was heavy surging and the occasional pop sound from under the hood (similar to a backfire). after about 10 minutes the problems disappeared, only to come back again about 15 minutes later. The plugs and fuel filter are new. Are these signs of my fuel pump dying... ?"

/ Posted by Chris92/

I didn't see any postings on what, actually, causes this trouble. The range of possible sources is quite wide:

1. Faulty coilpack
2. MAF
3. Knock sensor
4. O2 or PCV sensor
5. EGR valve
6. "Clogged cat." - I've never heard about this before. Is it really possible?

Has anyone overcome this problem, ever? If yes, could you please share your experience with others and narrow down this list? Please...

How would a car behave if O2 sensor or PCV is bad? Help, please....

 

if the o2 sensor is bad then it will run either too rich or too lean. wont cause the popping sound. at that milage the knock sensor should be replaced if it hasnt. this will only cause a loss of power after its warmed up again wont cause the popping. the MAF if its bad the car will stall or not start at all or just run REALLY bad, again no popping sound. clogged cat well if its clogged enough it could cause back pressure that may make the popping sound, if the coilpack are bad they could also cause the misfire and popping sound.

 

could be a dead injector also. they are sometimes intermittent like that your car will kind of vibrate at idle and have a loss of power. proboly not the cat when mine went my car got progressivly slower over 1 month

 

I've been going through this same type of thing....

-replaced the fuel regulater and filter
-replaced o2 sensors
-all plugs and injectors are clean and fine

I'm currently getting a new pump put in....hopefully that'll solve the problem. if not, it may be MAF next....hopefully not.

I'll keep you posted.

 

Thanx guys for your input.

It really feels like "clogged cat." I'll let you all know what the hell is this as soon as I fix it.

Thank you all

 

One faulty coilpack will give you intermittant missing, stumbling under high loads such as heavy acceleration. Since coilpacks can be in varying degrees of failure you may get only one failing at medium acceleration, and 2 or more under heavier acceleration. Coil packs are an easy, but expensive fix. They run between $40 and $60 each (*6) at the discount houses. You can try visually inspecting them and replacing one or two that you suspect. If you're lucky, you'll be right. If not..... You can't test them by revving at a standstill since unless they're REALLY bad they won't break down unless they're under load. One or two faulty coilpacks could cause something that feels like "popping" as the car jerks and stumbles, but they won't really make a "popping" noise.

MAF problems can be difficult to pinpoint. There are many types of failure. Mostly a failing MAF will give you weird drivability problems like stumbling at odd times, poor idle, stalling when stopped and so on.

This also makes your car jerk and stumble under load, but typically most often once your engine compartment becomes warm. The knock sensor tends to read a knock easier when everything is warm and pull timing out and then put it back. Again, jerky but no real "pop". This is much harder to fix then coilpacks, but much cheaper (like about $120 vs $360)

A failed O2 sensor will cause your car to go into full rich mode. This usually make it run well, but with EXTREMELY bad gas mileage.

An EGR valve failure usually only makes you fail emission tests.

A clogged cat is usually the result of having a failed O2 sensor for a long time or using leaded fuel. Either can case the matrix to breakdown. In most cases when a cat fails the matrix breaks down and is blown out the tail pipe. In some cases though it does become clogged. This doesn't happen as often as it used to though. A clogged cat has the asme symptoms as any other cause of a plugged exhaust system. You'll notice a complete loss of power throughout the rev range ALWAYS with a exhaust sound like someone stuffed a potato in the tailpipe.

Things that you didn't mention that CAN cause "popping" noises include...

1. Bad or loose crank angle sensor causing mis-timed spark and mis-fires.

2. Timing chain or tensioner worn again causing mis-timed spark.

3. Worn intake valves allowing fuel vapor into the combustion chamber at improper times.

4. Hot spots in the cylinder head causing detonation.

5. If the "popping" is coming from further back then the engine compartment and it happens under deacceleration it could be running very rich (O2 sensor?) and backfiring in the cat.

In any case, get the codes from the ECU and do a compression test (wet and dry). Make sure to clear the ECU codes and then drive around until the problem happens again. Read the fresh codes then.

This will give you a clearer picture of what's going on.....

 

There are no codes, thuogh... Nothing.

It starts at around 1500- 2000 revs usually. Exhaust noise goes down, getting really quiet when it happens. I hardly can hear it as if it's plugged or wrapped with noise isolation stuff. The car slows down, popping sometimes. I got to floor
it to make it go... Then it may accelerate wildly and run good for a little while.

In about 15 - 20 min it starts doing this **** again.

 

If you can drop the cat and try to look through it. It may be getting stuffed from an over rich running engine

 

so the car runs fine for a short while and then starts to hesitate; occasionally under w.o.t. you get a backfire-like pop in the pre-cat area? the pop seems like overly-rich/detonation. the hesitation could be something else entirely. occasionally, i will get a pop, too, probably from overly-rich. but i have never encountered the hesitation problem. i even replaced the O2 sensor recently and still think i'm running slightly rich.

i will re-read the diagnostic stuff in this thread.

 

Gents,
It's over, I got it fixed.....
My lovely MAX runs like 2 years old wild born mustang ( It's 92 though... :-)))) )
All these power losses, pop sounds etc... Just because of - guess what...
Yes guys, O2 sensor even may cause intermittent pops. Weird? I know ti for Sure...
O2 sensor!!!!!!!

 

[QUOTE=gattonero]Gents,
It's over, I got it fixed.....
My lovely MAX runs like 2 years old wild born mustang ( It's 92 though... :-)))) )
All these power losses, pop sounds etc... Just because of - guess what...
Yes guys, O2 sensor even may cause intermittent pops. Weird? I know ti for Sure...
O2 sensor!!!!!!!

How did you come to the conclusion that it was the 02 sensor, did it throw a code, or did you test it?

 

Hi Chris92,

No codes, which is weird ... Just tried to narrow down the search area starting from less expensive or easy fix, before doing smthg like MAF ($400), injectors or coilpacks (~$100 each):

1. Changed Plugs,
2. Air Filter
3. Cleaned Throttle body, injectors (dealer)
4. Checked fuel pressure (dealer)
5. Cleaned EGR
6. Changed O2 - and that was it! I've been driving for a week already... Runs Excellent!



Did you fix yours? You got same problem... I guess...

 

O2 will not set a code until it has failed on OBDI cars.
It can be bad / slow and still be ok as far as the computer is concerned

 

I checked the pcv valve, egr valve, fuel pressure, trouble codes and all looks o.k., but like you say, yours didn't throw a code for the o2 sensor either. I swapped my 02 sensor about 2 years ago, I think it has about 50,000 kms on it. I did notice that I had a small vacuum line disconnected that runs to some sort of purge canister near the master cylinder. When I hooked it back up to the vacuum port, the vacuum operator that makes the butterflies within the intake manifold work started to work again. This is probably unrelated, but you never know. The car hasn't stalled out today, but I don't think the traffic conditions were the same today.

 

Your symptoms are EXACTLY as mine and I got it fixed...OK, O2 doesn't go often. 50K probably nothing, however, since this is not an expensive fix, I'd go for it and try...

 

This is funny because I put my new y-pipe on last week. During the process, the guy helping me kind of cleaned off my 02 sensor. I didn't think much of it, but it hasn't stalled since then. I even ran it at WOT several times to try and feel the added power from the cattman y-pipe.

I am not sure if this is a fix for the problem, but it is at least a strange coincidence. My car never "popped" or anything. It just stalled under heavy acceleration, acting like it hits the rev limiter.

I am not totally convinced this has solved anything, but there is always hope.

 

Chris,
trust me, your car will run fine until the meet. At that time the stalling problem will rear its ugly head, or it will wait until after the meet on your way home. Its just how they operate.