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idle hesitation(low rpm)

2K views 13 replies 6 participants last post by  scyclone 
#1 ·
its on the 91 b21, just got done with 90% of the car and close to gettin ready for emissions. got the header/full 2.25", brand new cat. "custom" intake going stringht down by firewall.sparkplugs/wires. fuel filter/readjusted all the cam clearances(142k no smoking yet). i couldnt be happyer with the car for now. but the only problem i got now is, the slight hesitation when accelerating under 3k rpm. the RPM slightly drop for like a fraction of a second before revving up. but this only happens when the car is warm. while its cold and beginning to warm up it very responsive. and also it sometimes idles high as 2.5k while cold but it usually drops to 1.2-1.5 quick if i press the clutch and shitf in gear and slightly moving the car. then it stays at that rate, and when its fully warmed up its at 800 or so.
any ideas what could cause this. my engine light used to be on till i cchanged the O2sensor (4-1 code i think it was). now its off and hanst come on since.

any help/ideas appreciated.
 
#4 ·
ok that makes sense, wires and plugs are brand new. cap/rotor havent checked yet also about timing. i dont have any tools to check that with . how much does a car shop usually charge for these?
 
#6 ·
Can't be the filters, they cause different problems.

I agree with dano on the ignition parts, if it isn't them then i'd head on to the TPS (no throttle enrichment), after that i'd look at the map sensor and it's vacuum line.
 
#7 · (Edited)
If you are asking about the cost of a timing light, you can get them for around $25 these days. They are very handy for tracking down bad plugs and wires as well as setting the ignition timing. Unless a shop is familiar with Hondas, I wouldn't let them set my timing. You need to jumper a service port before you adjust the timing and they may not know where this is.

If your problem started after you installed your brand new wires and plugs maybe one of the wires is not seated or maybe you have a bad plug.
 
#8 ·
Bobnova said:
Can't be the filters, they cause different problems.

I agree with dano on the ignition parts, if it isn't them then i'd head on to the TPS (no throttle enrichment), after that i'd look at the map sensor and it's vacuum line.
I guess I skipped over the part where he mentioned fuel filter... weird... and I don't see why it couldn't possibly be filters, but I think you're a mechanic so I'm not going to argue.

I agree about the TPS because one time I decided to drive my car with it unplugged and it did this... but I'm not so sure it would be affected by hot/cold...

What kind of spark plugs did you use? I hear plain NGK's are real good for these engines... and to stay away from platinum.

The high idle when engine is cold is normal...
 
#9 ·
On the filters bit, a severly clogged air filter will reduce engine power at high rpm (high flow) but won't affect anything else.
On older EFI setups, and carb setups, it will cause rich running, but not on a MAP system.
A clogged fuel filter will cause problems during sustained acceleration, it will flow enough fuel to run at low speeds, but in high flow/load situations it won't be able to flow enough.
Going uphill for instance, at high throttle.

If it were REALLY plugged it could cause problems at low speeds/load, but it wouldn't hesitate then go, it would just flat out not go.
 
#10 ·
Tecknixia said:
I guess I skipped over the part where he mentioned fuel filter... weird... and I don't see why it couldn't possibly be filters, but I think you're a mechanic so I'm not going to argue.

I agree about the TPS because one time I decided to drive my car with it unplugged and it did this... but I'm not so sure it would be affected by hot/cold...

What kind of spark plugs did you use? I hear plain NGK's are real good for these engines... and to stay away from platinum.

The high idle when engine is cold is normal...

looked around, and wasnt able to find why are other then NGKs plugs no good for our engines.? i have some bosch (not sure if they regular or platinum or w/e), bought them because thats all autozone carried for ma car unless i wanted to drive off 20 miles south for NGKs. wtf is the diffrence anyways a spark is a spark.
and btw it does the same thing with the bosch or the old NGKs that came in the car. also does the thickness of the wires matter,? i didnt buy those since they looked pretty new.and they dont fit like the stock ones theyre alot longer.
 
#11 ·
Hmm, well if it did the same thing with different plugs then I guess that's not it.

I thought you said you had new wires... but you didn't get them? huh? NGK also makes wires for our car that fit and have the different lengths for better look. I'm pretty sure that's them in Jay Jay N's sig. If you can't find good parts locally, you can sometimes find good deals online. I got oxygen sensors (2), wires, and plugs all NGK for $132 at sparkplugs.com.

NGK Premium wire set
9593 (stock number)
HE54 (part number)
1 (quantity) $35.00

Next step I would try distributer cap and rotor. I think all you need for that job is a philips screw driver.... hmm, maybe 10mm socket, either way it's real easy, just a simple unbolt and rebolt.

About the spark plugs, I'm not sure why some are better then others, but I've heard to not use platinum, hopefully someone else can explain that... and I'm sure it's in other threads, maybe you'll stumble across it.
 
#12 ·
....shit, i dont like to start new threads but i must mension that after cleaning out my distribuitor cap and everything i dont have that problem. but instead somtn else came up.

i finally got it registered and today was my first day on the road,:-D
imagine, after warming it up, i took it for a little drag on a secluded road, Problem now is tthat the motor DIES it simply refuses to accelerate after 4-4.5kRMP its like its out of gas or somtn, same as taking your foot off the gas, id first look at my fuel pump but i dont have $1 to spend till tuesday next week. wut a bitch, ....im so dissapointed.
 
#14 ·
TPS was out of place..wierd, it seems to roatate just like the distribuitor, i just moved counterclockwise all the way (facing the front of the car) and problem is gone. does its position affect performance or just ability to accelerate?
 
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