I have noticed that at times(1 out 5 starts) it takes a couple tries with key to fire up. Majority of the time it cranks at the turn of the key. I cleaned the mass air sensor, cleaned the trottle body, changed plugs, checked and had no codes. I only have 71K on our 2000 Expy 5.4L. Only mods are superchips programmer, e fans, 3" exhaust, and K&N drop in, Mobil 1 since 5K . Could this be one of the COPs? Last year when I changed the plugs for the first time I noticed some green coating on the blade of the COP, either on the #3 or #4. I cleaned it(scraped on it some), but I didn't remember to check last weekend when I changed plugs again.

Any suggestion to check on is appreciated.

Thanks,
Rob

 

Clarify: Does the engine crank normally during those attempts when it fails to start or does the cranking demonstrate any sluggishness or other irregularity?

If it acts normally but still fails to fire, I'd suspect either diminished fuel pressure (use a guage to measure) or a sticky IAC valve.

Try cracking the throttle 1/4 way on every start attempt until you can determine if there is a change in the frequency of the failure to start. If it starts reliably with the throttle cracked, you can bet on the IAC being sticky (very common). If it still fails to start intermittently, investigate the fuel pressure to see if it is abnormal.

If the cranking is irregular or sluggish during failed starting attempts, I'd suspect improper fuel synchronization.

If a COP were intermittent, you'd most likely have a rough running engine after startup along with a CEL and a misfire code.

Steve

 

By cranking I mean the motor is spinning over. I turn the key for a second and it turns over several revs, then pull it back, try again, sometimes it starts and sometimes it takes the third try. I did however kept the key turned for a couple seconds longer and it started. I'll pull and clean the IAC as it hasn't been off. I only cleaned the TB. butterfly and where it seals against the ID of the housing.
Thanks,
Rob

 

Well I took off the IAC and cleaned it. It really wasn't as nasty as what I have seen when I would do this on my 5.0 mustang. It was rather dry. At first it seemed to start right up, but here again about every other start I would have to crack the trottle and it fires right up. I guess it will need replacing.

Thanks,
Rob

 

Original battery?
On my old truck I gradually got used to cranking and cranking without actually noticing it was taking longer.

I eventually bought a new battery and it started like a new truck.

 

Raoul beat me to it. I would try a different battery. My 97 used to crank a time or two in the cold WX especially. I replaced the battery and it would fire right up. I mean turn the key and wham, she was on!

 

Battery is good(2yrs old). It spins the motor fast, just doesn't fire up at times.

 

What is an "IAC" and where is it? My truck is doing this.

 

Idle Air Controller

A common problem with these trucks.
If I tried to type all the info I'd leave something important out.
The IAC has been discussed in detail, often.
do a SEARCH in the ENGINE forum , phrase = (IAC)

 

I just tried that search and hit the 500 limit.

When you search select "Thread Titles Only" this will return 80 threads that more than cover the IAC topic.

 

Thanks, I'll check it.

 

Okay, I bought a new IAC week before last and just had time to change it out this past saturday. I didn't drive it until yesterday for some errands. It started up fine for the first 3 occasions, but when I when to start it at the grocery store it didn't fire up on the first try, It did after I turned the key again. I got home and turned it off and then again and it started on first try. I washed it( even though it was 50F here in Houston-it needed it) and started to pull it in the garage no problem. We pulled it out again later and it cranked right up.

Anyone have any suggestions on where I can look that would cause this intermittent problem.

I don't have any codes, plugs are new, battery is good, idles good and runs very strong?

Thanks,
Rob

 

My 01 screw is doing the same thing, I had to take my car to work this morning because it wouldn't fire up. It turns over ok but wont catch, it tries to then sputters and dies. This has been going on for about a week, sometime it fires right up and others it wont stay lit. If I hold the gas pedal down a little it cranks right up but when I remove my foot from the pedal it dies. Anybody have any suggestions other than the IAT? Also can the IAT be picked up at a local auto parts, I'm in Houston as well.

thanks

 

I picked it up at AZone for $40.00. Of course I have the old one that is most likely ok as its doing the same with the new one. I'll let it go very cheap.. $5.
I'm in Humble.

 

New plugs????