ibost

hello everyone i have been enjoying the site for some time now
after purchasing a 1988 jeep Cherokee Laredo 6 cyl 4.0 with aw4 transmission

I was having problems with it not starting very easy and then it would not idle very well at all so you had to stay with it and keep rpms up till the motor got warm then it would run fine. i suspected the TPS so i tested with volt meter and readings were not good

but before i got it changed out my wife went to go to work and couldn't get it
to start so i went out and managed to start it although it had very hard time getting started it was sounding as if it was misfiring and not getting gas
but once warmed up it ran as normal so she took off got one block and it died on her i restarted and now it was doing same when starting and once got started and reved up it would idle fine but put into gear and press gas and it would just die over and over

so i pushed it into the driveway and i changed out the TPS, and fuel filter as well just incase it was the problem

but now its hell to get it started once it is it idles better then it every has
seems TPS fixed that.

and when i drive, its like idle real good put into gear and alls fine but give it gas and it wants to die. if just barely give it gas it goes okay

but cant give it very much gas or it just stalls

whew!! long winded but wanted to try and give as much info as poss.

ANY IDEAS?

desperate in Texas
Ibost

67 GMC

Did you adjust your TPS for the right voltage or just install a new one. You need to do that as well. Could be your fuel pump. I had a great running jeep that would bog down when you gave it the gas. Changed fuel pump and it's great now.

cruiser54

Also make sure that the vacuum line from the throttle body to the MAP sensor, on the firewall directly behind the engine, is in perfect shape.

That TPS needs to be adjusted with a meter as suggested. Checking CPS output would be a good idea also.

ibost

thanks for reply's
yes i did adjust the TPS
A to B was 4.85 and B to C was set to .08
as per http://autorepair.about.com/library/faqs/bl051i.htm

as i said was having real problem with idle on start/warm up of engine
that has now changed. idles quite well now
WHEN i get it started, which is very hard

ibost

also after morning coffee i intend to check out MAP
and try to find CO2 sensor to check it

CPS? what and where is it?

and as far as fuel pump.
is that in gas tank? and how hard to replace?

and this was a sudden deal was driving late the night before and was running just fine and that morning started this with hard to start stall when gas pressed

should add this did happen during a 3 day off on rain
but raining was over and water puddles gone by then but humidity very high still

cruiser54

Good chance your TPS is adjusted incorrectly.

Use these instructions and probe the flat 3 wire connector.


RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned. It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: With the Key OFF, and using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, some modifications to the sensor ground harness will be necessary. The harness repair must be performed before proceeding. I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION:
RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body. This manual transmission vehicle TPS provides data input to the ECU. The manual transmission TPS has three wires in the connector and they're clearly embossed with the letters A, B, and C. Wire "A" is positive. Wire "B" is ground. Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors. Note the voltage reading--this is your REFERENCE voltage. Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts. Adjust the TPS until you
have achieved this percentage. If you can't achieve the correct output voltage replace the TPS and start over.
AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-wire connector, same as the manual transmission vehicles have, and it is tested the same as the manual transmission equipped vehicles—FOR ENGINE MANAGEMENT RELATED ISSUES.
However, the automatic TPS also has a square four-wire connector clearly embossed with the letters A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module. THIS SQUARE FOUR WIRE CONNECTOR IS USED FOR TRANSMISSION/SHIFTING RELATED ISSUES ONLY. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage. If you can't, replace the TPS and start over. So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and the other side feeds the TCU.
FOR AUTOMATIC TRANSMISSION RELATED ISSUES: Check the four-wire connector side of the TPS.
If you have ENGINE issues check the three-wire connector side of the TPS. For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 08-27-2012

cruiser54

Here's a picture of the CPS. It's harness plug is near the firewall, on top of the intake manifold.

ibost

OK
That was a mistype on the .08
i meant to say .80
but anyway retested and reset it to .82
4.85 in x .17 is .82
so i reset it to .82 don't think it made any diff at all
also took loose the grounding lug at dipstick i cleaned and shined up all sides of all metal and re tightened it.

i put meter to CPS and got as follows
put ohm test to it and did not get continuity
put leads to the 2 wires going to CPS at connector and cranked over engine and did not get any voltage at all.

it said to set to AC volts seems like it should be DC volts?
tried both and still got no voltage coming from CPS when cranking engine.

So does this mean i need to replace the CPS?
and would that explain the problem i am having?

DFlintstone

Yea, it's defiantly AC volts, directly from the unplugged CPS you are checking. Around .3 and under defiantly sucks. .4 and up seems to do it. So you will have your Digital meter on it's lowest AC scale. On some of mine that's 200, (and only reads to tenths)(which works), and on another it's 2 V, which also reads 100/ths which is nice. Crucial part there, the CPS is the "heartbeat"!


If it's not cranking well, jump it for the test.

ohm's test is 200 plus/minus 75, hot. (from FSM)

ibost

what do you mean jump it for test?

get no ohms at all
and get no ac volts at all when i crank it over

also looked at the CPS and OMG!
it looks imposible to get to

DFlintstone

I just meant jump the Jeep, like you would with a dead battery, it it's not cranking "briskly".

Sounds like it's toast. If you are confident you have the meter connected, and on the right scale...They are a common problem.

11mm socket > 3 inch extension > universal > long (18-24 inches of extension). Your feet are sticking out under the passenger side, you can sort of reach up past the front drive-line with your left hand to hold the CPS. Your right hand is on the ratchet way back by the tranny cross member. If you tie a long string on the old, you can use it to haul up the new. Toss that piece of plastic if it's still there, and do not drop the bolts in there! Echlin # css980, (from Napa), should be fine, but some prefer to go to Jeep. I wouldn't bother with anything else for that!

If your left forearm is bigger than a quart Mason jar, you might conciser removing the front drive-line. Also You might cut your old wires because of that wire retaining clip, then be sure your new are held somewhere safe!

The second one is REALLY easy.

ibost

i have the new CPS on hold at Auto zone
are you saying dont buy it from them?
need to get part from jeep dealer?

DFlintstone

I myself would go with the Echlin from Napa, (I forgot to mention that..Napa), or the dealer. Just better odds!

It's not so bad. With the swivel and the long extensions, turning the bolts becomes possible. Me with the front up on ramps, I can just barely, with difficulty reach up past the drive-line to touch, hold the CPS with my left. Some might find that easy. Plan on taking your time. It IS a bit "surgical", but with the tips I'm passing on, you shouldn't shed a tear!

I don't think I would like trying to do it without the universal/swivel, and a bunch of extension.

ibost

Ok thanks for the info and tips

swivel and extensions are no problem
and i will go to napa for the part

my arms are defently to large to get up there but have a skinny armed
son that should be able to handle it

I will let you know how it goes

thanks again

DFlintstone

Yea! Do please get back to us....right arm no problem since it's down by the cross-member on the ratchet. Most people should not have too much trouble reaching up past the drive-line with the left.

Just . I hope you are sure. I have small alligator clips on my meter leads to touch those pins on the CPS connector socket. If your test was good, your CPS isn't, and the new will be sweeet!