Rough Idle
12-05-2008, 03:23 AM
#16
Race Car
To me it felt like it was running crazy rich during that time. I figure it is either a spark or fuel problem (i.e. no spark, or too much fuel). I had really low vacuum at cold idle (like 6-8" Hg) but no vacuum leaks at all and the ISV was operating properly (and the idle speed was okay when warm). The last few things I have it down to are DME temp sensor, FPR, leaking injectors or TPS.
On a N/A if you have this issue it shouldn't be the TPS, since that is only used at WOT and idle. Really, I have no idea what to go after next, but if you crack this one please share with everybody. I'm sure more of us have this issue than admit to it
12-06-2008, 01:27 AM
#18
Hot start trouble is fuel pressure leaking down. For me that was caused by bad FPR. Fuel pump check valve or bad injector will also do that.
Loud fuel pump can be caused by way high fuel pressure, caused by failed FPR, was for me.
Rought idle can be caused by way high fuel pressure. My idle got noticeably better after replacing FPR.
Measure your fuel pressure and leakdown. Maybe your new FPR is bad.
Loud fuel pump can be caused by way high fuel pressure, caused by failed FPR, was for me.
Rought idle can be caused by way high fuel pressure. My idle got noticeably better after replacing FPR.
Measure your fuel pressure and leakdown. Maybe your new FPR is bad.
12-06-2008, 03:46 AM
#19
Drifting
Thread Starter
like i said, I replaced my fuel pressure regulator in the summer when I put new fuel lines on and injector seals.
could be bad injectors as I didn't test them before putting them back in.
engien temp sensor was also replaced.
I noticed something else also. If I park it and the coolant temp as shown on teh gauge still is in the middle when I restart it after say 15 minutes it'll start running rough again until I drive it hard again for a couple minutes then it gets much better again.
after a long highway drive for example it idles much smoother. so I thought maybe the Oxygen sensor is getting heated up and working when I drive it hard, because the coolant temp being hot doesn't seem to be related to the engine running more smoothly. when I park it the exhaust cools much faster than hot coolant.
just my guess.
could be bad injectors as I didn't test them before putting them back in.
engien temp sensor was also replaced.
I noticed something else also. If I park it and the coolant temp as shown on teh gauge still is in the middle when I restart it after say 15 minutes it'll start running rough again until I drive it hard again for a couple minutes then it gets much better again.
after a long highway drive for example it idles much smoother. so I thought maybe the Oxygen sensor is getting heated up and working when I drive it hard, because the coolant temp being hot doesn't seem to be related to the engine running more smoothly. when I park it the exhaust cools much faster than hot coolant.
just my guess.
12-06-2008, 08:32 AM
#20
Rennlist Member
If turns back over after it is shut off, that normally means a timing problem. That is my experience with old cars. My corvair did that when I had the timing way off. Check your belts and especially you balance belt, vibration.
12-06-2008, 10:51 AM
#21
Addict
Rennlist Member
Rennlist Member
You can spray wd-40 or even water to look for vacuum leaks, or do a smoke test. The liquid will smooth out the idle when it flows through the leaking seal or gasket.
12-06-2008, 10:53 AM
#22
I am have a similiar issue (except your turn off problem) and sending out my injectors on Monday to be cleaned, replaced seals and balanced.
I would stop assuming and place a FP gauge at the end of the rail to confirm pressure. This will confirm your pressure up to the injectors.
I would stop assuming and place a FP gauge at the end of the rail to confirm pressure. This will confirm your pressure up to the injectors.
12-06-2008, 02:31 PM
#23
Drifting
Thread Starter
I doubt my timing belt is off. i had it checked and tensioned last year.
the car shuts off and then a split second later the dash lights come on again and the engine seems to run on on cylinder for a sec and then dies.
12-12-2008, 02:47 AM
#26
Drifting
Thread Starter
cool. I bet my injectors need cleaning also. Maybe I should put in a bottle of techron in a quarter tank of gas and see if that helps. I already ran a couple bottles of injector cleaner through last year but didn't notice anything. I also always fuel up with chevron.
but yeah my car is high milliage so it may need injectors cleaned. there are some cheap injectors on ebay sometimes (bosche injectors), says new bosche inectors and they're pretty good price. so maybe I'll buy brand new injectors in the future.
but yeah my car is high milliage so it may need injectors cleaned. there are some cheap injectors on ebay sometimes (bosche injectors), says new bosche inectors and they're pretty good price. so maybe I'll buy brand new injectors in the future.
12-12-2008, 09:20 AM
#27
--a leaky fuel injector, which a witchhunter-ing might correct, will also case fast fuel pressure leakdown and would lead to the longer hot-starts you are seeing. Be nice to know what your fuel pressure is doing...
12-12-2008, 01:24 PM
#28
Instructor
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Loud fuel pump sure hints at FPR (was for me).
O2 did make a bit of difference for me on my idle.
Also over the years, I did a lot of little things that helped . Everything you did seemed to make real (albeit incremental) differences for me.
Cleaning and balancing the injectors was pretty good. I seem to remember cleaning the grounds at the rear of the engine helped a touch. Last year I replaced the AFM (chasing a hesitation when very cold), and that smoothed out the idle the last tiny amount - perfect now (better be, nothing left).
Good luck.
O2 did make a bit of difference for me on my idle.
Also over the years, I did a lot of little things that helped . Everything you did seemed to make real (albeit incremental) differences for me.
Cleaning and balancing the injectors was pretty good. I seem to remember cleaning the grounds at the rear of the engine helped a touch. Last year I replaced the AFM (chasing a hesitation when very cold), and that smoothed out the idle the last tiny amount - perfect now (better be, nothing left).
Good luck.
Have you replace your injector O-rings or had them cleaned? You probably need to do compression and leakdown tests. Edit, just saw you replaced your O-rings on injectors.
12-12-2008, 01:41 PM
#30
here's my experience...
https://rennlist.com/forums/showthre...ferrerid=16010
Last edited by aben8057; 12-12-2008 at 03:39 PM.