1988 jeep vacume problem

Trevor Price · 08-07-2007, 05:40 PM

I put a new carbureator in my 88 jeep and it runs fine in park but when i put it in gear it ideals down and dies.

A friend said it could be the vac line that went to the transmission I think I found this line and traced it out but it’s capped off. Could this be the problem?

Pleases help my wont to drive my jeep badly

**qldit** · 08-08-2007, 07:14 PM

Good Morning Trevor, is that replacement carb properly compatibile with that engine capacity?

Have you adjusted the fuel/air mixture adjuster near the base of that carb for proper best idle when the engine is warmed?

Ensure any unused vacuum connections on the carb are properly blanked.

What was the reason for the carb replacement and is it identical to the original?

You may need to adjust the idle on the throttle arm to overcome that problem, there is some extra loading when drive is selected, but the no-load idle speed in park or neutral should not be excessive if any adjustments are made.
If idle air/tuel mixture is not properly adjusted the engine has no "grunt" at idle and could possibly be your problem.

Does that carb have an idle self adjusting vacuum device on the throttle arm?
Some carbs do and it marginally increases idle if there is a shift in engine vacuum.

Others will have different ideas.

Cheers, qldit.

Cheers, qldit.

dai · 08-08-2007, 07:31 PM

also check the height of the float

Trevor Price · 08-10-2007, 02:20 PM

Thank you for the replies.

Just wondering what the RPMs should be in park and in drive.

Should I adjust the idle when it is in park or drive?

How do I cheek the float, and how high should it be?

**qldit** · 08-10-2007, 05:13 PM

Good Morning Trevor Price, generally you will find it easiest to adjust the idle speed in Neutral or Park when the engine is warmed, and work on the principal of keeping a reasonable idle when drive is selected.
Further adjustment may be needed after you determine if that works under all conditions for a day or so.
Use commonsense with the actual idle RPM, don't have the engine racing in neutral or thump or try to move the car off when drive is selected.

As a general rule of thumb, float level in most carbs is in the order of a half inch to five eighths below the top of the reservoir lip. But generally new replacement carbs are preset so I would be careful.
Check your vehicle service manual for precise information.

Cheers, qldit.

Trevor Price · 08-10-2007, 06:38 PM

I got it to run well by turning the idol up to 13000 RPMs when it’s in park. Then when I go to Drive it drops down to about 9. Should it drop this much From park to drive? And is it bad for it to tac that high in park?

**simpswr** · 08-10-2007, 06:50 PM

13,000 Rpm ????

Trevor Price · 08-10-2007, 06:55 PM

my bad 1,300

**qldit** · 08-10-2007, 08:00 PM

Good Morning Trevor Price, 1300 RPM at idle sounds a bit high to me, I would expect something in the order of 800 or that kind of area, but if you are watching your vehicle tacho it may well be showing incorrectly, so it is a case of commonsense type of approach.

If thase figures are correct it possibly indicates the engine is pretty sick, possibly low on cylinder compression.

It may be worthwhile doing a complete cylinder compression check and see what it is in comparison to book figures.

Why did you replace that carb, was it for gutless kind of performance?

Others will have different ideas.

Cheers, qldit.

Trevor Price · 08-11-2007, 02:10 PM

I got the idle down to 800ish but it drops down a lot when I put it in gear.

I cheeked the timing and it jumps around allot I got it were its in about the middle. Dose anyone knows why it jumps around so much?

Also should I adjust the choke?

**qldit** · 08-11-2007, 04:18 PM

Good Morning Trevor Price, on many of those vehicles when you set your timing you need to disable the vacuum advance on the distributor, usually just pull the vacuum line off at the distributor and plug the hose. Erratic vacuum can be very misleading.
The actual settings and procedure may need to be obtained from the service manual.

When you get that kind of fluctuation if it isn't being caused by the vacuum advance system it can also be caused by a worn distributor, so if it still jumps around when the vacuum is off, you might inspect for worn distributor shaft or other items in it.

The choke should be fully off when the engine is warmed and anytime idling adjustments are made, although there may be an interaction with the throttle arm and the choke mechanism to marginally increase throttle arm position when the choke is applied.

It sounds like you are well into the learning curve there.

I have a sneaking feeling your engine may be down on cylinder compression, this would account for a larger than normal drop in engine speed when drive is selected.

When compression is low the power differential at lower engine speeds can be a real pain to try to overcome.

Most often when this power loss is the case it is caused by engine valves and seats needing to be reworked.

Others will have different ideas.

Cheers, qldit.

08-07-2007, 05:40 PM	#1 (permalink)
Trevor Price Registered User Join Date: Aug 2007 Posts: 6 OS: xp	1988 jeep vacume problem I put a new carbureator in my 88 jeep and it runs fine in park but when i put it in gear it ideals down and dies. A friend said it could be the vac line that went to the transmission I think I found this line and traced it out but it’s capped off. Could this be the problem? Pleases help my wont to drive my jeep badly

08-08-2007, 07:14 PM	#2 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: 1988 jeep vacume problem Good Morning Trevor, is that replacement carb properly compatibile with that engine capacity? Have you adjusted the fuel/air mixture adjuster near the base of that carb for proper best idle when the engine is warmed? Ensure any unused vacuum connections on the carb are properly blanked. What was the reason for the carb replacement and is it identical to the original? You may need to adjust the idle on the throttle arm to overcome that problem, there is some extra loading when drive is selected, but the no-load idle speed in park or neutral should not be excessive if any adjustments are made. If idle air/tuel mixture is not properly adjusted the engine has no "grunt" at idle and could possibly be your problem. Does that carb have an idle self adjusting vacuum device on the throttle arm? Some carbs do and it marginally increases idle if there is a shift in engine vacuum. Others will have different ideas. Cheers, qldit. Cheers, qldit. Last edited by qldit; 08-08-2007 at 07:16 PM.

08-08-2007, 07:31 PM	#3 (permalink)
dai Manager, Hardware Forums Join Date: Jul 2004 Location: west australia Posts: 56,637 OS: win 7 32x 64x rtm	Re: 1988 jeep vacume problem also check the height of the float __________________

08-10-2007, 02:20 PM	#4 (permalink)
Trevor Price Registered User Join Date: Aug 2007 Posts: 6 OS: xp	Re: 1988 jeep vacume problem Thank you for the replies. Just wondering what the RPMs should be in park and in drive. Should I adjust the idle when it is in park or drive? How do I cheek the float, and how high should it be? Last edited by Trevor Price; 08-10-2007 at 02:21 PM.

08-10-2007, 05:13 PM	#5 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: 1988 jeep vacume problem Good Morning Trevor Price, generally you will find it easiest to adjust the idle speed in Neutral or Park when the engine is warmed, and work on the principal of keeping a reasonable idle when drive is selected. Further adjustment may be needed after you determine if that works under all conditions for a day or so. Use commonsense with the actual idle RPM, don't have the engine racing in neutral or thump or try to move the car off when drive is selected. As a general rule of thumb, float level in most carbs is in the order of a half inch to five eighths below the top of the reservoir lip. But generally new replacement carbs are preset so I would be careful. Check your vehicle service manual for precise information. Cheers, qldit.

08-10-2007, 06:38 PM	#6 (permalink)
Trevor Price Registered User Join Date: Aug 2007 Posts: 6 OS: xp	Re: 1988 jeep vacume problem I got it to run well by turning the idol up to 13000 RPMs when it’s in park. Then when I go to Drive it drops down to about 9. Should it drop this much From park to drive? And is it bad for it to tac that high in park?

08-10-2007, 06:50 PM	#7 (permalink)
simpswr Moderator Hardware Team Join Date: May 2007 Location: Houston, Texas Posts: 12,264 OS: XP, Vista, Win 7	Re: 1988 jeep vacume problem 13,000 Rpm ???? __________________ Rich MemTest86 \| BenchTest \| Virus/Trojan/Spyware Help How to post a Screen Shot \| PC running slow?

08-10-2007, 06:55 PM	#8 (permalink)
Trevor Price Registered User Join Date: Aug 2007 Posts: 6 OS: xp	Re: 1988 jeep vacume problem my bad 1,300

08-10-2007, 08:00 PM	#9 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: 1988 jeep vacume problem Good Morning Trevor Price, 1300 RPM at idle sounds a bit high to me, I would expect something in the order of 800 or that kind of area, but if you are watching your vehicle tacho it may well be showing incorrectly, so it is a case of commonsense type of approach. If thase figures are correct it possibly indicates the engine is pretty sick, possibly low on cylinder compression. It may be worthwhile doing a complete cylinder compression check and see what it is in comparison to book figures. Why did you replace that carb, was it for gutless kind of performance? Others will have different ideas. Cheers, qldit.

08-11-2007, 02:10 PM	#10 (permalink)
Trevor Price Registered User Join Date: Aug 2007 Posts: 6 OS: xp	Re: 1988 jeep vacume problem I got the idle down to 800ish but it drops down a lot when I put it in gear. I cheeked the timing and it jumps around allot I got it were its in about the middle. Dose anyone knows why it jumps around so much? Also should I adjust the choke?

08-11-2007, 04:18 PM	#11 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: 1988 jeep vacume problem Good Morning Trevor Price, on many of those vehicles when you set your timing you need to disable the vacuum advance on the distributor, usually just pull the vacuum line off at the distributor and plug the hose. Erratic vacuum can be very misleading. The actual settings and procedure may need to be obtained from the service manual. When you get that kind of fluctuation if it isn't being caused by the vacuum advance system it can also be caused by a worn distributor, so if it still jumps around when the vacuum is off, you might inspect for worn distributor shaft or other items in it. The choke should be fully off when the engine is warmed and anytime idling adjustments are made, although there may be an interaction with the throttle arm and the choke mechanism to marginally increase throttle arm position when the choke is applied. It sounds like you are well into the learning curve there. I have a sneaking feeling your engine may be down on cylinder compression, this would account for a larger than normal drop in engine speed when drive is selected. When compression is low the power differential at lower engine speeds can be a real pain to try to overcome. Most often when this power loss is the case it is caused by engine valves and seats needing to be reworked. Others will have different ideas. Cheers, qldit.