Stalling under decel/rough run and idle
01-15-2017, 07:48 PM
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Stalling under decel/rough run and idle
First time posting, first time owning a cherokee. Came from a 1997 tj. I now have a 1988 2dr, 4.0, 5sp manual cherokee chief. It's stalling after upreving and rapid let off/decel and running very rough at idle. I've nearly replaced everything, including the whole distributor unit and I'm pretty sure the timing is right. But, after hooking up a meter to break booster, and checking vacuum, it's all bad. So, I guess I have to two options. Is it a retarded timing problem? Or should I go through the entire vacuum lines and manifold. Anyone have advice where to start? I don't want to mess with the timing if it's a vacuum problem, and I don't want to try and find a leak if it's a distributor/timing issue. Any help would be great, thanks.
01-16-2017, 01:41 PM
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Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
Cool! 2 door 5 speed...On top in my signature is a link to Cruisers tips. Strongly recommended you look at 1 through 5. Good steps even if it seemed to be OK. Also there are Napa part #'s for Renix vacuum stuff as well as a bunch of stuff I thought was nifty. Tossen out a couple ideas below;
There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage and it will be pig-rich. (maybe black smoke, fouled black plugs). You can pull the line off the MAP and feel for vacuum with your finger. If it runs!
Vacuum leaks suck. I go around with short little shots of starting fluid, if you hit one the sound of the engine will change. Small little shots! You don't want that stuff to accumulate. It's a fire hazard, but It evaporates right away. Also with a tube, or a section of hose you can listen for it. Don't forget the lower O rings on the injectors need to seal as well. (uppers would leak fuel).
The manifold bolts have a habit of loosening, especially that rear one. On anything like that you never want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I go over about three times. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep. ALSO, there is a large line coming off the intake, rear of the TB that goes back to the firewall, across, then forward down to the vacuum ball behind your right front bumper. You can pinch that off or unplug it and cap the nipple to test if you have a leak there. The line to the break Booster can also leak vacuum.
There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage and it will be pig-rich. (maybe black smoke, fouled black plugs). You can pull the line off the MAP and feel for vacuum with your finger. If it runs!
Vacuum leaks suck. I go around with short little shots of starting fluid, if you hit one the sound of the engine will change. Small little shots! You don't want that stuff to accumulate. It's a fire hazard, but It evaporates right away. Also with a tube, or a section of hose you can listen for it. Don't forget the lower O rings on the injectors need to seal as well. (uppers would leak fuel).
The manifold bolts have a habit of loosening, especially that rear one. On anything like that you never want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I go over about three times. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep. ALSO, there is a large line coming off the intake, rear of the TB that goes back to the firewall, across, then forward down to the vacuum ball behind your right front bumper. You can pinch that off or unplug it and cap the nipple to test if you have a leak there. The line to the break Booster can also leak vacuum.
01-17-2017, 09:18 AM
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Cool! 2 door 5 speed...On top in my signature is a link to Cruisers tips. Strongly recommended you look at 1 through 5. Good steps even if it seemed to be OK. Also there are Napa part #'s for Renix vacuum stuff as well as a bunch of stuff I thought was nifty. Tossen out a couple ideas below;
There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage and it will be pig-rich. (maybe black smoke, fouled black plugs). You can pull the line off the MAP and feel for vacuum with your finger. If it runs!
Vacuum leaks suck. I go around with short little shots of starting fluid, if you hit one the sound of the engine will change. Small little shots! You don't want that stuff to accumulate. It's a fire hazard, but It evaporates right away. Also with a tube, or a section of hose you can listen for it. Don't forget the lower O rings on the injectors need to seal as well. (uppers would leak fuel).
The manifold bolts have a habit of loosening, especially that rear one. On anything like that you never want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I go over about three times. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep. ALSO, there is a large line coming off the intake, rear of the TB that goes back to the firewall, across, then forward down to the vacuum ball behind your right front bumper. You can pinch that off or unplug it and cap the nipple to test if you have a leak there. The line to the break Booster can also leak vacuum.
There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage and it will be pig-rich. (maybe black smoke, fouled black plugs). You can pull the line off the MAP and feel for vacuum with your finger. If it runs!
Vacuum leaks suck. I go around with short little shots of starting fluid, if you hit one the sound of the engine will change. Small little shots! You don't want that stuff to accumulate. It's a fire hazard, but It evaporates right away. Also with a tube, or a section of hose you can listen for it. Don't forget the lower O rings on the injectors need to seal as well. (uppers would leak fuel).
The manifold bolts have a habit of loosening, especially that rear one. On anything like that you never want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I go over about three times. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep. ALSO, there is a large line coming off the intake, rear of the TB that goes back to the firewall, across, then forward down to the vacuum ball behind your right front bumper. You can pinch that off or unplug it and cap the nipple to test if you have a leak there. The line to the break Booster can also leak vacuum.
01-17-2017, 09:19 AM
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01-17-2017, 02:49 PM
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Year: 90,84
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Engine: 4.0,2.5
Firstly it's actually a MAP. Second, testing it first would make sense. Third they don't seem to fail often. Really all the original Renix sensors seem to be pretty robust. Canning an OEM sensor, then installing Chinese crap from AutoZoned is not so smart usually.
01-17-2017, 03:56 PM
#6
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Well I would start with the vacuum harnesses first:
http://amzn.to/2k26tNx
http://amzn.to/2k2bfKG
Then I would make sure all your bolts are torqued on your intake/exhaust manifolds. I had a similar problem and it ended up being a blown intake/exhaust gasket.
also look up nick in time films:
https://www.youtube.com/channel/UC_8...PVI69FPc76y6lw
He has a lot of good info, and has developed a engine monitor that he's sold betas of, and is rolling out more as time goes on. so keep an eye out. I LOVE mine and it has already helped me solve several issues.
http://amzn.to/2k26tNx
http://amzn.to/2k2bfKG
Then I would make sure all your bolts are torqued on your intake/exhaust manifolds. I had a similar problem and it ended up being a blown intake/exhaust gasket.
also look up nick in time films:
https://www.youtube.com/channel/UC_8...PVI69FPc76y6lw
He has a lot of good info, and has developed a engine monitor that he's sold betas of, and is rolling out more as time goes on. so keep an eye out. I LOVE mine and it has already helped me solve several issues.
01-17-2017, 07:17 PM
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Thank you for all the suggestions, trying everything this weekend. Also, how would one test and see if the MAF sensor is working? Unplug it while the motor is running and see if it makes a difference? I agree replacing the old trusty American made stuff with Chinese junk is bad, but if it's broke, it's broke. And working is better than nothing.
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01-17-2017, 07:51 PM
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Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
The MAP, itself is very rarely a problem. The stupid brittle tube from the TB to it breaking is a very common problem. In here is a basic test. There is a more through test involving using an analogue meter, (with a needle), and a vacuum pump to watch the "swing" in voltage. The MAP itself is not somewhere to spend much time. Following Cruisers 1 through 5 on the other hand is something anyone with a Renix should consider. (OK 89 and 90 don't have a C-101 connector, so it's less than 5 for them)
Some sensor diagnostics here>>> http://www.lunghd.com/Tech_Articles/...iagnostics.htm
To correct my self above...both the 02 sensor and the TPS are known to fail.
Agreeing with "circles" once one of mine once spit out pieces of it's exhaust man. gasket.
Some sensor diagnostics here>>> http://www.lunghd.com/Tech_Articles/...iagnostics.htm
To correct my self above...both the 02 sensor and the TPS are known to fail.
Agreeing with "circles" once one of mine once spit out pieces of it's exhaust man. gasket.
Last edited by DFlintstone; 01-17-2017 at 07:57 PM.
01-17-2017, 08:45 PM
#9
CF Veteran
if you buy the two things I linked to, it comes with a new hose for the map sensor. its $45 for the set, and worth every penny to not have to worry about those hoses anymore.
and then buy a new manifold gasket, and just replace it. Actually buy a whole gasket kit, and replace as you have time:
http://www.rockauto.com/en/moreinfo....179839&jsn=434
and then buy a new manifold gasket, and just replace it. Actually buy a whole gasket kit, and replace as you have time:
http://www.rockauto.com/en/moreinfo....179839&jsn=434