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Another engine stumble problem.


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Has anyone experience of/ a cure for a slight hesitation between touching the throttle and the revs actually picking up?

It seems that the engine actually dies for a fraction of a second after touching the throttle and then picks up normally. The engine does not stall, but it does cause a delay in pick up and hence a reduction in accelleration when moving up through gears. The problem is more pronounced when cold, but doesn't totally disappear even when warm. The TPS is showing 0 (fully closed) at idle according to freescan and since all of the inlet system (plenum to inlet manifold and all in between) is new, then I have no concerns in this depatment.

For reference, the engine is in good shape, is running standard chip ('89 SE) in the ECU and has the origional injectors (though WC engineering injectors are awaiting installation along with a #3 chip). EBPV removed and its vacuum pipe blocked.

Any clues?

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i think the same problem on mine was caused by the idle below 1000 cutting out cylinders thing. read in the freescan manual somewhere that under 1000, the ecu starts cutting out cylinders (V8 US thing for emissions etc). i tried a new MAP sensor too, but i have ended changing just about everything to get it to run right. if u are going to fit a later chip, these all idle higher than 1000, so the problem goes away. mine still does things like that now and again, it got a mind of its own. even with the throttle jack physically disconnected, it still cold starts at 2000 revs sometimes too.

think i also set the TPS to as high volts at 0% as possible, as mine was too low. maybe there is some lag when the throttles are just opened, if the TPS is not spot on

then again, it could be ICV related. some numpty had wound my minimum air rate screw in to try and get it to idle, after they had mullered the ICV. it was bent half way along, and the o ring was missing.

hope thats of help......

PS, change that chip, you'll love it.

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even with the throttle jack physically disconnected, it still cold starts at 2000 revs sometimes too.

Mine too, zackly the same, rarely though so i'd kind of forgotten about it.

The TJ used to do it all the time and the first time it happened without, i

thought it must have grown back or something...

:blink:

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Has anyone experience of/ a cure for a slight hesitation between touching the throttle and the revs actually picking up?

<{POST_SNAPBACK}>

Was doing some experimenting the other day to make sure my fuel pump had enough fuel volume and pressure to cope with all the modifications I have done to the engine.

My engine was suffering from the symptoms you are describing. So to eliminate some variables I jumpered the fuel pump relay (at the relay mounting block) right across where the relay prongs #30 and #87 would go. This eliminated computer control of the fuel pump. :blink:

The "bogging" symptoms off idle totally disapeared, and the general running and drivability are now very good (no complaints). The difference before and after was very obvious. This is the point where I actually first looked at the fuel pressure gauge, and of course, everything was perfect. When I looked at the insides of the removed relay, it didn't look too bad, but there was some wear on the contacts.

I'm not yet done with my fiddling, but in my case, it looks like marginal electrical connections may be affecting the fuel pump performance.

Cheers.

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