jerybak

I noticed the other day that from idle i was getting a stumble, not sure where to start looking.

Hope this video comes thru on the post. Let me know.

FredR

For purposes of clarity, is the problem something that has suddenly degraded noticeably or is it a characteristic that may have been there previously but were not aware of?

My initial reaction [flawed as it may be] from your video was that you may be expecting too much by snapping the throttle open the way you were. Perhaps I can put it a better way by asking when driving normally, have you noticed anything different recently with the pedal response?

Rgds

Fred

jerybak

It is something that I have recently noticed, yes from a stop light if you punch it, you can feel the hesitation/ stumble.

Under normal driving conditions, it does not present any stumble or hesitation, it seems it only occurs from idle and under a quick hard acceleration from idle.

Crumpler

Hey J, it was hard for me to pick up a pattern on the vid.
I couldn't tell if it was stumbling or just hunting a little.
You can check resistance on your TPS at WOT and idle, and see if it is in spec.
Did you guys replace that?

jerybak

no we didnt change the TPS, only hall. its a stumble/ hesitation.

FredR

Ok- as long as you are not chasing your tail as it were-it invariably boils down to either fuel or ignition related issues

Fuel side:
1. Have you changed specific fuel that you use recently or have the fuel station you normally use changed supplier and/or made a seasonal variation to the fuel blend?
2. O2 sensor- is that known to be in good shape?
3. Have you checked the fuel pressure regulator and both dampers for smell of gasoline on the vacuum side?
4. Any signs of a vacuum leak [fast or unstable idle].
5. LH computer failure can do some strange things- can you change out with a known "good one" to eliminate the obvious.

Ignition side
6. How old are your ignition leads- any signs of spark tracking to earth if you look under the bonnet at night time? - particularly so if you look around and under the distributors/coils.
7. I doubt it will be a coil issue- those tend to break down at mid to higher range rpm's but..?
8. Check the condition of the contacts inside the distributor cap?

Doubtless there will be more but hopefully some useful suggestions to consider

I doubt it is anything to do with the idle switch contact but you can try to ensure the contact is making and breaking normally [not usually a problem on the idle contact]

Rgds

Fred

SeanR

Best quick guess is that it's running a bit rich and it's bogging down as it gasps for air. Just a guess though

jerybak

Fuel:
1. no same fuel, same station since I bought it
2. this has not been verified, when X pipe was installed we did not change it.....(should I have changed it then?)
3. i have gauge installed on the rail, 3.5bar, holds pressure for 30-60 mins after shut down, have not check for gas smell as regulator & dampers are less than 6months old
4. idle is stable, i plan have engine smoke tested soon, but i don't think any vac leaks are present
5. guess I need to secure a loaner on this....ANYONE? I am running 24lb injectors and PorKens chip set

Ignition:
6. all new beru leads less than 6 months/ new plugs also
7. not sure on coils, that is one thing that the PO had done
8. contacts looked good on TB/WP job last month.

jerybak

how can i best diagnose this rich fuel condition?

byrdman454

Get the air/fuel ratio meter from Daddio or maybe the dyno can check it Friday.

byrdman454

Also...if it turns out to be a rich condition it might be the first signs of your LH failing. If I recall, you said it was not a rebuild. My LH went wicked rich when it finally failed. I don't know if it happens all at once or not, though.

jerybak

I spoke with the owner of the dyno shop we are doing tomorrow, he will do fuel/air form a tailpipe probe. I will also see about the meter when I get the LSD from Daddio.

Does anyone have an 87 LH laying around?

byrdman454

I think my '88 will work to try. If you are going to replace it, just get a rebuild from JDS. Let's see what the results are from your dyno first.

jerybak

if we are screwing around with the LH, guess we should replace the 02 & install Daddios meter in the glovebox.......928 = ME

byrdman454

The dyno should tell you the rich/lean condition so you really don't need the meter unless you just want it...

Check with Crumpler on where he mounted his Friday. I think he has one in his car.