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[JamesH]

Need help on the question that's probably lost in my build thread (see below): Is it likely to be the cheapo TPS I fitted and should I get a Mopar one? Or could it be another sensor or something mechanical? It's really pissing me off now 


Question - bad idle, really bad splutter / hesitation,  TPS changed, no blocked CAT, crank and cam sensors replaced not long ago with Mopar ones. No fault codes last time I scanned but I didn't scan again today. Ignition components not old and v low miles on them. Won't rev above 3k rpm. Has moments of perfect idle but it's not driveable. Should I start looking at mechanicals? Compression?

[wildwood]

Two TPS and the throttle body from me no good? Oh dear

Got mine from Lighties as they now do one that they guarantee.

[JamesH]

Two TPS and the throttle body from me no good? Oh dear

Got mine from Lighties as they now do one that they guarantee.

Wrong connectors for my XJ unfortunately. Interesting about Lighthouse, maybe worth giving them a call.

From being in the Jeep at Cheapfest you almost immediately said it was likely to be TPS so that's the direction I've been heading, now I'm just worrying it's something else and maybe more difficult / sinister 

[gazjeep]

Rock auto mate ?

Your RockAuto discount code 1770003515075638 will expire on December 8, 2013.

[j33pky]

Funny that... Lighthouse sold me crown and told me it wouldn't work then got me a mopar one that did...

[JamesH]

Is it worth speaking to them then?

The dealer will take weeks, Rockauto are quick but probably just Crown and equivalents. Lighthouse do next day if it's in stock

[Nosebolt]

Rockauto will give you a list of manufactures and quick, my O2 sensors were here within 48hrs plus cheaper even after taking postage into account, just be aware that if you order more than 1 item that they come from the same warehouse or you get 2 transport charges

[gordy]

Rock Auto.

[JamesH]

I'm a big Rockauto fan but they don't do a Mopar TPS and I've already bought an aftermarket one that has made no difference (possibly worse).

I tried Lighthouse by no answer so I think I'll call them tomorrow and discuss the issues and maybe they can get me a Mopar one like they did for j33pky.

j33pky - any idea or explanation why the Crown one wouldn't work?

[j33pky]

Andrew said they were hit or miss... Or shit.  £115 ish for a mopar one

[j33pky]

But it worked straight out of box

[Dtimot8]

Do you get JP magazine the symptoms you describe are an exact match to those that they describe for the MAP sensor
the article is called driveway diagnostics
they even say that it wont through fault codes
have a look at their website
I'll scan the article tomorrow just in case
Regards tim

[JamesH]

Worth a try I suppose Tim, thanks.

Any electrickery gurus know if I van test the sensors and how - I have multimeter and obd2 scan tool but no oscilloscope.

[willo]

I'd also look at upstream and down stream o2 sensors....

can you not splice the wildwood tpa onto your xj harness? i had to do this a lot on my engine swap, the plugs were different between years

[Mike2909]

I have a spares one of each taken from XJs .If you want them for the postage (plus a beer) I will send them to you. I took them from the scrappys for my ZJ which was cured of similar faults by replacing the MAP sensor.

[JamesH]

Mike - Sounds good, can you check if they have round or flat pins for the connectors first please?

Will, I could yes but I'd need the correct plug or would be bodging with electrical connectors and tape. I might do something like this just to test it. Unless I'm being dumb about it of course and missing the easy way to do it.

[bluevanman]

if theres just 2 wires a multimeter should show if theres any dead spots just set it to resistance. cheapo analogue meters work best .

[bigjeepzj]

The TPS has three connections on it
a pos one side neg the other and the centre is the variable one.
put a meter between the centre and neg move the throttle and the voltage should change with the trottle

[willo]

Ah. I have it a bit confused. You need the sensor and flying lead

[JamesH]

The TPS has three connections on it
a pos one side neg the other and the centre is the variable one.
put a meter between the centre and neg move the throttle and the voltage should change with the trottle

Tested this morning - got nice steady increase in signal voltage from 0.6v - 3.8v closed to open with no obvious blank spots using a digital multimeter and opening the throttle very gradually and allowing the meter to register.

Do you know if the voltages are correct? The supply voltage is 5v and disconnected the signal wire has 4.6v

My instinct is that this is ok and that I should change the map sensor but reassurance would be nice.

[Jonny Jeep]

The signal voltage is 12 to 76% of the 5V supply which is fine. My scan gauge shows mine as 14 at idle and 74 at WOT.

Since 98 models have just one upstream O2 sensor you can disconnect it. That will force the computer to use it's programmed fuel tables. If it runs OK with the sensor unplugged the sensor is usually (99%+) the cause of the problems.

[gazjeep]

Is the one on a 98 TJ the same ?

If I can find my spare, I'll bring it to TH

We replaced the 2 oxygen sensors, TPS & cleaned up the contact to the fuel tank at the fuel tank end, got rid of all our rough running, o2 sensors seemed clean enough so cant be 100% what was the problem or a combination
 

[Dtimot8]

Hi James
heres the pdf's
if you look at the last caption it describes you issue perfectly
Regards Tim

[JamesH]

Excellent work guys, MAP sensor ordered as it seems highly likely to be causing the problems and that description of the crap running from the JP article is exactly my symptoms.

The 02 sensors aren't old and the symptoms are worse than when I had problems with the original one before and replaced it but I may come back to this if the MAP sensor doesn't fix it.

Gaz - sensors are probably the same, mine is a 98 and has flat blade connectors for all the sensors - other Jeep connectors are round pin connectors. The replacement TPS seems fine, O2 sensors are unlikely to be the prob just cos they are newish and I've only just removed the fuel tank pump assembly and cleaned it all up (but I could have damaged something re-fitting it of course!

I'll report back as soon as the sensor gets here and I can fit it.

Thanks again, I owe you all a few beers for chipping in with the advice.

[Mike2909]

Mike - Sounds good, can you check if they have round or flat pins for the connectors first please?

Will, I could yes but I'd need the correct plug or would be bodging with electrical connectors and tape. I might do something like this just to test it. Unless I'm being dumb about it of course and missing the easy way to do it.

The TPS have  flat pins.