98 Volvo s70 glt- 182k miles, engine re manufactured after timing belt broke at 126k

Problem: When at stop lights or just in park the car randomly hesitates for 1-2 seconds from 1k rpm to 500rpm and goes back up to normal 1k. It never does it while accelerating, or slowing down, only in "park" or at stop lights while in "drive" while idling. It has never stalled though. and no CEL!

I have done the following in attempt to resolve this issues and none of my attempts have been successfull.

1. replaced pcv system and cleaned ptc nipple
2. have kept throttle body clean
3. transmission flush
5. cleaned MAF sensor(it is not new, will replace eventually)
6. cleaned idle control valve

I will note when i replaced my spark plugs, the one plug had oil at the bottom. my mechanic said its nothing to worry about.....

Next project is to replace fuel pump and filter. they were last done 60k miles back, but the problem has existed for at least the last 20k miles maybe more. anyone having this issue and solved it? please share the info and i will do a write up and a youtube video for it if the fix is successful.

 

I had a similar thing happen to my 240 wagon. I replaced the really dirty fuel filter and it stopped right away. If I would stop too hard coming up to a red light, it would stall out and be difficult to start up, hopefully that is not happening to you. Correct me if I'm wrong, but your s70 has a distributor cap? If it does, have you been up to date with tune ups? I don't have a distributor cap on my s70, but my 240 does. My 240 runs beautifully, but it really lets me know when its time for a tune up. As soon as I do it, it runs like new. hope this helps!

 

yes, i have a distributor. it was changed less than 60k miles back so i have assumed it is good. would you recommend that be changed? and fuel filter also? I am leaning towards a possible vacuum leak or the MAF sensor.....

 

I always do a tune up around 20k on my 240, but that is a much more old fashion engine so it requires more attention than the s70. However, If your car is acting up like that it might be time to change it and the plugs. It might also be a good idea to swap the fuel filter, maybe you had a little debris in your gas tank and it's now caught in your fuel filter. It's possible you could have a vacuum leak, but if you haven't done a tune up in 60k, i'm sure that can't be helping either. Another thing I could think of that could be causing this is the air filter, it should be perfect if you changed it recently, but it's worth checking if you haven't. good luck with the problem and please let me know how it works out.

 

I am in the same situation with my 98 C70. It kind of chokes when idling sometimes, but runs smooth while driving with no CEL codes. Ive replaced my spark plugs, wires, ignition rotor and coil. I have yet to clean the throttle body, MAF or idle control valve..however I am leaning towards the problem being my fuel filter. I know the car sat for a few months before I bought it so it may be clogged.

 

Yeah, I bet its the fuel filter that's clogged. It always seems to "choke" when braking before an intersection right?

 

i havent noticed it during braking, its only during idle. When im in "Park" or in "Drive".... while at a stop. it would be a different situation if it was choking on acceleration or braking, which is also a common problem, but not my problem. i ordered a new distributor and plugs and fuel filter which ill replace this week and ill let ya know if it goes away. ill be really happy if thats all it is!

 

ohhhh. i see what you mean. I'm sure the fuel filter is playing some sort of role in the stalling

 

My car does sometimes seem to choke/misfire when im braking as if the gas is having a hard time coming through the fuel filter. I am waiting for my new filter to arrive and hopefully solve the issue.

 

so i changed my fuel filter, and it was in bad shape but i still got the hesitation during idle. im at wits end! Im thinking it the MAF but dont want toshell out for it if thats not the issue! any other ideas? could it be a small vacuum leak? ive checked the elbow on the right side going to the engine and its in good shape.... possibly the fuel pump or fuel relay??

 

I also changed my fuel filter which helped some, but the rough idle still came back from time to time. I ended up having to replace the evaporative purge valve and canister shut off off valve and hosings attached to the gas tank. Since this proceedure, I have put about 300 miles on my car without a hickup FINALLY!!

 

so its been quite a while since ive posted any updates on this topic. the problem persists! ok in the last year ive replaced:
fuel pump
fuel relay
fuel filter
alternator
spark plugs
ignition coil
MAF
timing belt and tensioner
water pump
all belts
radiator
and not to mention all brakes/suspension components
have not done any work on the turbo...possibly the culprit?
im currently at 216k miles and still getting the hesitation on idle at stop lights and when in park. some have said replacing the ignition coil fixed their problem but i just did mine 2 days ago and still have the hesitation. NO CEL!
anyone else perplexed?

 

Could be a cam or crank sensor wanting to fail or some other electronic part that just hasn't gone out. It's sad when there is a gremlin.