Cold starting issue with truck

[captmello]

Hey I've got a question about my trusty tow vehicle (also my daily driver).


I've got a '96 F150 4.9ltr. Always starts, 25 below, no problem.

Here's the issue.

When its 20 dgrees or warmer the engine starts and goes into a high rpm idle for a warmup period.

When it gets colder, down to zero maybe. The high idle takes a few seconds to kick in. If I release the pedal it may die. I hold the pedal down enough to keep it running and after a few seconds, it idles up to normal high warm up idle.

When its below zero the higher idle doesn't kick in at all. I have to sit and hold the pedal for a few minutes to keep it from killing and once it will idle on its own it never goes into the higher idle mode at all.

Anyone have any ideas?

 

[Bob_VT]

Re: Cold starting issue with truck

Is it fuel injected? I have had the 4.9 with a carb and I just had to keep the choke flap free so when I first stomped the pedel it would close the choke.

I am not sure what controls the cold start in the FI model.

Are you running E-10 gas? If not hit it up with some dry gas too.

 

[Bob_VT]

Re: Cold starting issue with truck

I have been thinking about this....

I am pretty sure you have a throttle body.... is it clean?

Have you run any techron fuel system cleaner in the tank. There is a possibility all the injectors are not firing right due to dirt.....it is a 1996.

I have alway found the best thing for the older engines is fresh plugs and a cap and rotor. The 4.9 is a quick and easy change

Probably one of the best 6 cylinders made with great tourque......

 

[captmello]

Re: Cold starting issue with truck

Thanks Bob,

Ya its F.I. runs really good 231K, I've had this problem for three years

Just don't know where to begin. I drive over 100 miles a days. Always fresh fuel. New fuel pumps, filter, recent tune. Runs perfect.

The only thing it does have is a bad exhaust manifold gasket, but I don't think it would relate.

I wonder if a sensor would cause it behave like that? Cold start sensor? Any such thing? Working in reverse?

Thanks again

 

[Bob_VT]

Re: Cold starting issue with truck

Bad gasket...... isn't the intake and exhaust gasket integrated? I absolutely hate that set up and they are tough to seal properly.

If you have a bad gasket then it could be waiting for the heat from the warm up to seal properly...... think about that.

 

[Docknocker]

Re: Cold starting issue with truck

Don't discount the bad exhaust man. gasket. On my '96 F350 (Intl 7.3 diesel),
exhaust temp partly controls fuel volume for cold weather starts.
Not a mechanic, but maybe something similar on gas engine, and a leak could effect sensor temp?

 

[captmello]

Re: Cold starting issue with truck

Thanks guys,

The exhaust does quiet down as the engine heats up, Thats why I believe it to be a bad gastet not a cracked manifold. Been that way since I got the truck.

Bob, they very well could share the same intake and exhaust manifold gasket. I'm still not sure why this would effect it. You think I may be leaking at the intake as well and pulling air through, leaning it out?

 

[Bob_VT]

Re: Cold starting issue with truck

Yes I do. I watched a mechanic tighten bolts on an inline 6 intake and exhaust and with every click of the wrench the engine was running better.

You do have an O2 sensor and that helps the mix/settings too and until that is receiving a good reading it is running wrong.

The WORST part of changing that intake/exhaust gasket is making sure you do not snap off or crack any of the tabs that the bolts pass through. Many mechanics will shy away from that gasket set because it is such a PITA

 

[captmello]

Re: Cold starting issue with truck

I wonder it I could tighten the bolts on mine? I might just snap off the studs in the process.

Thanks again for your thoughts.

 

[chiefalen]

Re: Cold starting issue with truck

Warm the engine first, then shoot the bolts with pb blaster. Let it sit and shoot them again and let them sit, while they are sitting shoot all the cable and everything up top bye the linkage and everything that moves when you hit the pedal, good to have a helper bribe the wifey to help.

Then tighten carefully the bolts. Real easy when warm the motor they should tighten 1/4 to a half a turn each.

Good luck be careful alot of mileage on that truck.

I might be picking up a older ford myself cheap. Always wanted a pickup.

This one i'm looking at has over 2 hundrend thousand also.

 

[david_r]

Re: Cold starting issue with truck

yes a bad gasket will have an effect on all sorts of stuff--- o2 sensors for sure.


if you can get the bolts out without breaking them , go to the parts store and buy a thread tap and clean out all the threads and you will cut your chances of breaking a bolt during re-assembly in half.......a complete tap and die set is a little pricey but well worth it.....they are a lot more usefull than you think.

also while you are under the hood check ALL your vacuum lines.

by the way that straight 6 will out pull a 5.0 all day long...........when i was working at ford i kept asking how come they quit producing those, but never got a straight answer.....of course i doubt ford would even give up the secret to any dealer.

all i can figure is ford wasnt making enough money on parts so they got rid of one of thier best engs.........although im a chevy man i worked at ford and own 2-----but theres no denying that 300 is hard to beat.

 

[puddle jumper]

Re: Cold starting issue with truck

I don't know if anyone has mentioned this yet. Try cleaning your throttle body/AIC motor assembly. The AIC motor might be sticking on till the engine heats up.

 

[chiefalen]

Re: Cold starting issue with truck

Straight 6 great running keep the oil clean and will run forever. Bullet proof also, and your right they never made any money on them once they left the factory.

But the 351 CLEVELAND now that is a motor, seen them go over 300 thousand no problem and still run strong i never seen one go bad except the body goes on the car before the motor. Thats why you see them in the junk yard.

Don't confuse it with the Windsor, that motor i never liked.

 

[captmello]

Re: Cold starting issue with truck

thanks for all the Helpful thoughts!!!

I'm not sure what I'll do next. Cleaning the throttle body/AIG Motor can't hurt.

I may try tightening the manifold like Chief suggested but am a little nervous about making things worse by breaking bolts etc. I'll have to get some of that PB Blaster. It always starts and runs great. the exhaust gasket leak is not loud and has been there since I got the truck. I don't think its worth the effort to change out the gasket just to see if it fixes the cold start issue.

I also had a '91 F150 with a 351 F.I. Not sure if cleveland or windsor. I ran it up to 215K. Drove it to the junkyark with a broken frame and multiple issues. That motor would make that truck jump. Much more power than my 300.

We see how the weather goes this weekend, maybe open the hood and take a look around. Can't go boating.

 

[puddle jumper]

Re: Cold starting issue with truck

I had the Cleavland in my 73 Torino sport. What a rocket.
My brother and dad both had the 300 six. Fantastic engines.

 

[dolluper]

Re: Cold starting issue with truck

As Pj said dirty IAC or not adjusted.....he said aic......when cold vehicle works on computer pre-sets till operating temp then O2 sensor controls with info provided to it......on warm upTPS and CTS are more of the factors

 

[captmello]

Re: Cold starting issue with truck

Hummm...

I'll look in my haynes manual, see if it points the AIC motor out to me, sounds like its right in the throttle body. I'm not a pro so bare with me on the abbreviations. TPS I know, throttle Pos. sensor, CTS, not familiar, nor AIC.

I know the check engine light works, would any of these parts, if dirty, or not getting good info, cause a check engine light? The light is not on. Can the TPS and the CTS be cleaned/ Adjusted?

Thanks again for the input guys!! I'll try to spend some time on it today and see if helps in the coming week.

 

[BaileysBoat]

Re: Cold starting issue with truck

Iac.

 

[captmello]

Re: Cold starting issue with truck

BaileysBoat, thanks for the correction. Too bad you couldn't tell me what it stands for, probably be easier to remember. Have you any useful advise for a simple carpenter?

 

[captmello]

Re: Cold starting issue with truck

Idle air control