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ray1111 12-13-2010 04:48 PM

Gettin Upto Speed on Hiway Sputters @ 50mph
Hey all, I'm new to this site but have owned my 93 YJ Wrangler for about three years. I've gotten by with repairs but this one has me and friends baffled.
I have a stock 93 YJ, 2.5, manual tranny. When I leave my house and get on the highway, which is only 1/4 mile away, and try to get up to speed, at around 45 - 50 mph it starts sputtering real bad. It does clear up sometimes. But, it doesn't do this all the time. I can drive around town fine. It starts and idles great.
I have replaced the fuel filter, distributor and rotor cap. I did notice that when I changed the fuel filter, there was no pressure in the line.I did a check engine light blink test and it only came up with code 12 and 21.
I guess the code 12 is battery power to PCM disconnected is standard because the engine isn't running. The other 21 is the oxygen sensor or circuit.
Any suggestions would be greatly appreciated.

JDGROVER 12-13-2010 04:56 PM

is it like its not firing on all cylinders?

ray1111 12-13-2010 05:07 PM

It acts like it is running out of gas is my best analogy. It's not like it loses fire on one or two cylinders. The first time it happen I made it to the gas station to put gas in it and it ran fine till I got home about 20 miles away.

crunch 12-13-2010 05:29 PM

Maybe your fuel system isn't venting right and its building up a vacuum in the tank. after you filled up it ran fine for about 20 miles what I am thinking is you broke the vacuum when you filled up and after 20 miles it built back up. try running with out the cap on and see what happens.

ray1111 12-13-2010 05:47 PM

I'll give it a try and let ya know. Thanx

ray1111 12-14-2010 05:26 PM

I just tried it without the gas cap and it didn't make any difference. Actually it seemed as though it's gettin worse.
It was worth a try. I would take it to a garage but having been laid off for almost 2 years sorta crosses that choice out.

jeepinmichguy 12-14-2010 07:16 PM

Soulds like a clogged cat. Either drill out your cat or have it replaced if your state has inspections. I had the same issue before and that was the culprit.

ray1111 12-14-2010 07:43 PM

I will give the cat a try now. LOL. Thanx
I also need to mention that when I replaced the fuel filter, a friend said to be careful cause there will be pressure when I disconnect it. Well, there was no pressure that I could see.

SandyMushYJ 12-14-2010 10:20 PM

I would do a fuel pressure test. Some parts stores will rent you a fuel pressure gauge, 100% refundable upon return. I am more familiar with the Chevy's, but with MPI, I would think you would need 35+ psi. My fuel sprayed all over when I changed my filter. Could be a failing fuel pump or leak in the pressurized line inside the tank.

livs 12-14-2010 10:40 PM

I saw another thread like this and had the same problem but I had it at all speeds.. It was water in the fuel line, so I put in dry gas.. Solved my sputtering problem. Only happens in cold weather, it's like two bucks for the bottle I would try it before any expensive repairs, worth a shot. You can get it at any auto parts store or gas station.

ray1111 12-15-2010 04:41 PM

I couldn't find anyone in these two towns that could do a fuel pressure test. I called a major Chrysler-Jeep Sales and they wanted 80 bucks for a test. I looked up Advance Auto and they have the pressure gauge for 42 buck. I'm thinkin of goin out and buy one.

I've already went thru almost 2 bottles of dry gas and 1 bottle of injectoin cleaner.

Tomorrow I'm goin to cut out my cat and go get that fuel pressure gauge and go from there.

Thanx for the replys gang. Every little bit helps.


ISUSteve 12-15-2010 06:23 PM

A lot of auto places have loaner tools; I know Advance Auto here does. They are free to borrow as long as you return them.

SandyMushYJ 12-15-2010 08:40 PM


Originally Posted by ISUSteve (Post 926252)
A lot of auto places have loaner tools; I know Advance Auto here does. They are free to borrow as long as you return them.

Exactly; Autozone, too. You usually "buy" the tool with the understanding that it will be returned for a full refund. Done it several times. Just walk in and tell them you need a loaner or rental. On the other hand, Ray, a fuel pressure gauge is not a bad tool to have if funds permit.

White-Lightning 12-16-2010 08:38 AM

I just fixed this problem on my jeep. It turned out to be the TPS. I got a new one at AutoZone for $35.00. Hope this helps.

ray1111 12-16-2010 03:35 PM

I have an Advance Auto local and they said they didn't have that to rent out. They are the ones that will sell me one for 41.99. I just need to know if the 93 YJ has the Schrader valve test port. I know where it is, I just don't know if that is what it's called.
Thanx for all the great replies gang.

SandyMushYJ 12-16-2010 03:43 PM

Should be a Schrader valve on the fuel rail, and Chilton's says it should be about 39 psi w/engine running.

RandomThoughts 12-16-2010 03:57 PM

Happened to my '97 (5spd 4cyl). It started at 45 (off and on) then got progressively worse/slower. I could drive around town at first, then... not so much. The tone of the exhaust changed and there was a odd smell. A few weeks beforehand I heard the catalytic converter "death rattle", but mistook it for a loose shield and didn't check it out before I started to have a problem. Changed the converter and it is right as rain.

It mildly upset me as a converter is a bit above what I can fix by myself with my current tools and location. Ah, well, C'est la vie.

Merry Christmas... RT

ray1111 12-16-2010 05:09 PM

I bought a fuel line tester.
To do a test for my fuel pump my Haynes book says to pinch off the return line momentarily to get the pressure upto 95psi and immediatly turn off the engine and let it set for 30 minutes to see how much pressure drops. Either I am totally illiterate or just plain stupid, but I can not determine which line is the return on this 93. Almost 4yrs of college and you would think I'd be able to read of book. Ugh!

SandyMushYJ 12-16-2010 07:02 PM

On most fuel-injected engines, the supply line is slightly larger than the return line. Maybe 5/16" supply and 1/4" return. I will try to find a location description via Google before I brave the rain to look under my hood.

ray1111 12-18-2010 12:05 PM

Well I just took off the exhaust system and totally wiped out the inside of the cat. It still does it. I'm gonna have to go google the fuel return line pics and see if I can't find it and do that last test with the fuel line pressure. If anything, I'll go and open up my 8x8 inch hole I made in the back above my fuel pump just in case it did go out and pinch it off there.
Thanx for the help gang.

Frenchie 12-18-2010 02:05 PM

What rpms are you in when the studder begins and it may be your map/mass senor

ray1111 12-18-2010 02:40 PM

The lowest gear/rpm that I had it mess up in was 4th at problably 2000. Other than that it's usually in 5th at around 2500 rpm give or take a few. I can jump right on the highway here at the house and it usually don't do it until about 2-3 miles. I can still drive around town here fine.

Frenchie 12-18-2010 04:08 PM

It doesn't sound like a fuel issue to me...sounds more like a sensor to me other wise around town would be a issue and it would happen right off the bat not abit down the road.

ray1111 12-18-2010 05:39 PM

Appreciate it Frenchie. What sensors do I start with? Like I mentioned before here, I would just jump into it and start replacing everything but bein laid off for 2 years doesn't help that at all.

ray1111 12-19-2010 07:24 AM

I neglected to say that this didn't happen all at once. I had it happen one day then two days later it happen a little bit. Now it's everyday.

ray1111 12-19-2010 08:00 AM

This is what I've been lookin at TPS:
Duralast/Throttle Position Sensor (TPS318) | Throttle Position Sensor | 1993 Jeep Wrangler 4WD 4 Cylinders P 2.5L MFI |

and this:

Duralast/Vehicle Speed Sensor (SU394) | Vehicle Speed Sensor |

Could these be possibilities?


ray1111 12-21-2010 05:05 PM

So far it has turned out to be the Coolant Temp Sensor. There are two heat sensors on my jeep; one on the block for the temp gauge and one by the thermo for the computer. I changed the one by the thermostat.
I took my ol' YJ out on the highway and ran the crap out of it tryin to make it do it again but it wouldn't. I'm goin to try and drive it to work tomorrow which is bout 20 miles away and see what happens.
Thanx everyone for you replies and suggestions.


SandyMushYJ 12-21-2010 07:05 PM

Well, now, teach us something: What led you to try a CT sensor?

ray1111 12-21-2010 08:28 PM

Actually it was a guy from another forum that mentioned it. He put it to me this way.
"Have you tried the coolant temp by the thermostat?" My reply was no, never thought of it.
His reply was, "Replace it then buy me a beer."
I replaced it and now I owe him a beer.
Before I replaced I thought about it and it does sound a bit logical. After thinking about it, when I took the jeep straight to the highway it was always at the same distance that it started to act up. At that distance is when the engine would be warming up and the cts not working would not be send the correct signals to the computer.
Well, like I said, so far it's working: Time will tell.

SandyMushYJ 12-21-2010 08:32 PM

I have heard of drivability problems caused by the CTS, but I never thought about it. I love my Snap-On Solus scanner, but it makes me think less.

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