strange hesitation/stumbling

AKDisco

Member
Sep 2, 2008
21
0
Kodiak, Alaska
www.myspace.com
Hello everyone,

Just thought I'd post here about a problem I've been having w/ my '95 Disco.

The engine has this strange hesitation on initial throttle tip-in, but this only happens when you start the engine after sitting overnight. There have been a couple times pulling out of the driveway where the engine hesitated/stumbled enough to stall. If you keep your foot on the throttle, it will stumble/hesitate for a second then 'clear up' and you're on your way. And it only does it pulling out of my driveway, and for the first few stop signs in my neighborhood.

Once the engine has run for a few minutes, the hesitation disappears and the Disco runs just fine and dandy. Subsequent restarts during the day are not affected by this strange hesitation - it only happens after the vehicle has been sitting overnight.

So far, I've checked the timing and vacuum advance, changed the spark plugs, wires, cap and rotor, fuel filter, replaced some leaky vacuum lines, and checked the coolant temperature sensor resistance. All seems ok there.

I've got a feeling that I might have a problem with the IAC (idle air controller) valve. If you rev the engine slightly on initial startup, the idle speed will drop too low and will take a bit before settling on high idle. As it warms up, the idle speed starts to come down - settling at a fairly normal 750ish once fully warmed up. I'll probably pull it out and see if it needs cleaning...

What do you guys think?
 

AKDisco

Member
Sep 2, 2008
21
0
Kodiak, Alaska
www.myspace.com
Well, I removed and cleaned the IAC yesterday. It was pretty nasty!

This morning, the hesitation/stumbling was still there - but it's definitely considerably better...at least it doesn't feel like its going to stall on me taking off from a stop sign. And it doesn't last nearly as long either. So that's definitely an improvement!

I'm thinking that the IAC has become slow in its age (appears to be the original 135k 1995 unit), so I may just replace it anyway.
 
B

bluejayrover

Guest
You may also want to pull the stepper motor and clean that. That did the trick for me many years ago. My 95 D1 has almost 200K on it.
 
B

barefoot

Guest
are the 95's injected? if so....look for leakdown through the night.
 

AKDisco

Member
Sep 2, 2008
21
0
Kodiak, Alaska
www.myspace.com
barefoot said:
are the 95's injected? if so....look for leakdown through the night.

Yup, my '95 is injected. The old injectors were leaking down quite badly - 3 of the 8 injectors leaked, and would bleed off the fuel pressure within 2 mins!

The injectors I installed were holding pressure just fine overnight...but that was a couple weeks ago. I'll have to check again and see if something has changed - you never know since these were used injectors...