Maters sick and i need help.

[Juggernaut31]

Okay go figure. on the wifes new 02 sport 4.0, when i test drove it, it started and ran like a champ, beautiful. the issue is/was, i drove it late in the evening. what i have found since then.

when you do a cold start, i.e. it has been turned off for say 7-10 hours, then when you start it, it goes dead.

if you feather the gas pedal (air only i know), but like you used to do, in the old carb models, you can keep it going. take your foot off, and it dies.

Once it warms up, it runs/idles perfect. starts perfect. no problems. let it sit in the parking lot until after work. see steps above.

I have cleaned the iac, cleaned the air intake, (it had a lot of carbon built up in there) see very very heavy black carbon, oh yes, and it spits back, like one does when it is fuel starved at cold start. but after engine is warm. it's perfect.

no SEL light on (probably out). i have searched, and have not found anything on here that is "exactly" like this. any ideas?

Most things tell me, if it does it cold, it should do it warm.

Just for clarification (cold) starts = Florida, 65 degree mornings, and 90 degree evenings.
Thanks guys, i need help, still broke from buying this thing for her. And i dont want her unhappy with it.

 

[dominicun1]

well im gonna be the first to take a wild guess and say fuel pump might be malfunctioning, and im only saying this because i recently had to replace mine. your cold start problem sounds very familiar however the only difference is that mine woudln't start. i picked up a used one from a junk yard for about $28, and she purrs like a tiger!...just a thought...anything helps!

 

[Juggernaut31]

Yes i agree, what i don't understand is that, as soon as it warms up, it runs perfect, and starts before you can even get your hand off the key. idles perfect, everything. it is just when it is cold. (not really cold) just hasnt been started, for a few hours.

 

[Dave 1955]

Maybe you're not getting enrichment when it's cold?

I hear guys say that there are two temp sending units. One for the gauge and one for the puter..might want to search that.

 

[tenny]

make sure BOTH temp sensors are good.

if it happends when cold ONLY.....then its a sensor issue

the fuel pump does not know when the motor is hot or not.

you need to look at fuel trims when cold and when hot,
see whether or not its fuel starved when cold......if so.....
its got to be a temp sending unit.

you also need to scan the truck, see if any codes are in there.

 

[2000StreetRod]

check the fuel pressure

The symptoms may be because of time sitting instead of cold temperature. The fuel pump could be weak and not pressurizing the system rapidly. The check valve maintains pressure in the system for several hours masking the weak pump. My fuel pressure only drops from 62 psi to 30 psi in more than 10 hours. If you don't have a fuel pressure gauge then try cycling the ignition on/off/on a few times before cranking the starter when the engine is cold. If the engine fires right up and idles correctly then the problem source is fuel pressure not engine temperature.

 

[Juggernaut31]

i know it isnt fuel, the pump comes on for only a second. cycling, or even continued starting makes no difference. only after it warms up a bit, then it purrs like a kitten. also i sprayed carb cleaner all around the intake, all vacuum locations, etc. and no change there. i did find i could removed the TPS, and even move the inside of the TPS, and it made no difference of how the engine ran. I agree i need to have it scanned. and find the locations of the two temp senders.

 

[sloop]

streetrod makes a good point - you have time passage and temperature - don't discount either

i wonder if it is related to the engine being 'in the loop' - doubtful because i think the engine has to be pretty hot for that - or maybe it is stuck in the loop at cold startup and it should not be

 

[Juggernaut31]

My next question is...... where are the two temp send. located on the 4.0? i am a complete newbie on the 4.0... quite different from my 5.0, or my previous 4.6

 

[sloop]

i think the second temp sensor is for the outside temp display only - its driver's side front down low, as best i recall

 

[2000StreetRod]

temperature sensors

As previously posted by Dave 1955 there are two temperature sensors on the SOHC V6. One sensor, the engine temperature sender, drives the temperature gauge on the instrument panel and has absolutely no impact on how the engine runs. The other sensor, the engine coolant temperature sensor, provides data to the PCM. The PCM enriches the air/fuel ratio when the engine is cold. The sensors are located on the thermostat housing.

If you don't have the one piece intake manifold it will be hard to access. The easiest way to test it is to datalog the engine coolant temperature via the OBD-II port.

Please explain more about the TPS not making any difference. Are you talking about starting, idling or driving? The TPS "tells" the PCM all kinds of important information: idling, accelerating, decelerating, WOT.

 

[4pullingGM]

I would bet that your intake gaskets are leaking. I replaced tons of those gaskets when I worked at the dealer. I know you said that you sprayed around looking for leaks, but those intake gaskets, rubber seals actually, shrink up when cold causing a leak. When it warms up they expand and seal properly so they aren't detectable then. Maybe have somebody keep it running while you spray around them on a cold start and see if you can tell a difference. Let us know what you find!

 

[Juggernaut31]

Okay thanks everyone. I did test the intake gaskets, NO LEAKING THERE. I installed a new TPS, and was an instant improvement. Now on cold start, where before it took at least ten minutes to even get it started and keep it running "Barely" it starts first time, and as long as you keep it running the first oh 5-10 seconds, it runs great, just a little hesitant on startup (just slightly though). I pulled the entire housing (as shown in ther pic above, and found that one of them temp sensor locations was leaking) (it had a slight water leak when i bought it, and i knew about this.), and so 145.99 plus tax, and i have a new one, and am putting it back together now. we will see how that works out. also just a side note, when i tested after the TPS i had not cleared the puter of codes. this time it will have been unhooked for at least 2 days, so i just be able to start with a fresh slate on codes.

 

[4pullingGM]

Sounds good, keep us up to date!

 

[Juggernaut31]

Sure will. also this weekend i replaced the back 4 body mount bushings. it had that slamming body/frame thing going on. now she rides as quiet as a church mouse.
Progress continues.

 

[Dave 1955]

Just a plug here for the scanguage 2.
I bought one and love it.
You can monitor all kinds of things. MAP..TPS..water temp that the pcm sees...plenty more.
Also it is a trip puter.
You can see codes and even pending ones.
You can clear codes without unhooking your battery. Speaking of that,unhooking your batt to clear codes is not a great idea..your pcm loses acquired perimeters doing that.

 

[Juggernaut31]

Yes i know that, and i didnt unhook it to "clear codes". i unhooked it in order to replace the thermostat housing. i needed to move the Alternator wire out of the way in order to remove the old one. clearing codes is just an added bonus. then i will have a clean slate "IF" anything pops up.

 

[Juggernaut31]

Okay Maters all better, and after a week of my wife driving it to and from work, all is well. Turns out it was indeed the intake gaskets. When i sprayed the carb cleaner around it, it was already warm, (so it would stay running, while i tested it). and of course, then it wasnt leaking. finally i was able to keep it chugging, long enough to try it again. it perked right up. so a trip to o-reilly's auto parts, $17.00 and some change, two and a half hours later. she cold starts, perfect, and purrs like a kitten all the time. Times are good.

 

[4pullingGM]

Excellent news

 

[Juggernaut31]

I can continue with this thread. My wife sold it and bought a Mustang. (very nice). and I have had two vehicles since I sold the Juggernaut. So I bought this one back, it has more issues now, but I liked it when she had it. so major overhaul. (paint/body/mechanicals/lift or drop) who knows. should be fun.