Crayfish03

I have a 1990 4.0l I6. When I am in neutral I can rev the vehicle as loud as I want with a little miss at first. When I put it in any sort of gear such as drive or reverse and try to hit the gas it will spit and sputter and never let me rev the motor to take off. I cleaned the TPS and Idle plug. Checked all vacuum lines to my knowledge and checked fuel pressure. Any suggestions greatly appreciated.

radicalvette

Have you checked fuel rail pressure or replaced the fuel filter. Your experiences seem to take place while under a load and even signs when not. Do you have any D.T.C.s stored or check engine light on. Check the exhaust pipe at the exit and see if its free flowing a plugged convertor can do this as well. Let me know good luck we have to come to a conclusion if its fuel air or a spark issue so right now we want to check fuel and a restricted exhaust like a convertor is not going to allow air in... im assuming you have a clean air filter or atleast not restricted right ?

Crayfish03

Clean air filter! Havent checked the exhaust but will in the morning. I checked the fuel pressure towards the end of the rail and some fuel poured out. Im not sure how much is supposed to come out though.

DFlintstone

*Anyone with an 87 to 90 Renix Jeep has two or three minutes to see that their CPS is putting out at least .35 AC volts. I don't mean to come off rude, but if you can't connect a meter and turn the key, we may not be much help. Easy as one, two three!
AC voltage CPS test; Small clips on the meter leads really helps. You need contact with those little pins while it cranks, maybe get someone to help.
#1 Unplug the connector at the back of the manifold with wires going down to the bell-housing/cps. (it's a three wire plug, with only two wires)
#2 Probe the two wires to the cps with the digital meter set on AC volts, a 200 scale on mine. Yours meter may have a lower 2 Volt, or “auto range”.
#3 Crank the engine and note the voltage. (jump it if your battery is low). .35 ( is minimum. .4 to .8 is more like it.
You can also check for 200 Ohm's resistance, +/-- 75, but the ACV is what the ECU is using.



Also right on-top in my sig.is a link to Cruisers tips. Great stuff there.

Also there, there are instructions on adjusting your TPS. Important, that.

Crayfish03

Ok so im confused on where i connect the probes. I do not have clips on my volt meter just spikes. where do i place them when i turn the key over

DFlintstone

#1 Unplug the connector at the back of the manifold with wires going down to the bell-housing/cps. (it's a three wire plug, with only two wires)
#2 Probe the two wires to the cps

You probe directly, the unplugged CPS. The probes will sort of stay in there,but it's way better to have help.

radicalvette

It shouldn't pour out it should spray out ... did you cycle the ignition switch to the on position before you pressed the schrader valve on the fuel rail ? Autozone has a fuel pressure tester kit you can borrow if you need to. When is rhe last time you replaced that fuel filter if ever ?

Bobolink

You won't have any DTC codes or a check engine light on your '90. Also you can't rely on the fuel squirting out of the schrader valve on the fuel rail as an indication of adequate fuel pressure. You need to put a gauge on it and check the pressure reading. With the engine idling, fuel pressure should be around 39 psi with the vacuum line disconnected from the fuel pressure regulator, and 31 psi with it connected.

Crayfish03

Thanks for the replies guys. I will work on getting a fuel pressure checker this week. But it has a brand new fuel filter but an original fuel pump.

firehawk618

It does get old and seems like this forum in particular is plagued with questions that are easily answered by reading for no more than 15 minutes on here.

radicalvette

Let us know... sometimes the preliminary checks solves a majority of issues before you get off to deep in left field. I tcan tell you from experience a bad fuel pump dialing in low pressure can make you chase your azz off if you don't eliminate and rule it out as the problem off the get go and it only takes a few minutes to do this.

aroundincircles

That is when I did it myself, My CPS was bad for sure.

radicalvette

Everybody is not as tech savy as others so and some don't know where to start to look so you just have to help them through the basics first and they will learn as they go and maybe next time know where to look and read.

radicalvette

What was the symptoms your jeep was given you ? Was it a no start or just running bad ?

Crayfish03

I am new to any sort of mechanics. Im only 20 years old so this is pretty new. I was going to do the CPS test today but I couldnt get a .2 amp fuse for my volt meter. And thanks for the vid! Ive also looked through cruisers tips and done the ones I understand. I dont want to go messing with stuff im not certain about. Dont want to take it to a mechanic either because im wanting this to be a learning deal as well.