First (legal) drive and engine issues

byroncobra · #1 (**permalink**) 05-08-2011, 11:18 PM

So off I drove on the weekend dodging showers and attracting attention....these cars aren't for the shy, retiring types are they.......dogs bark, girls smile and their boyfriends try and ignore you

Anyway, a small issue that I've been hoping might go away got worse on my first few trips.....upon startup everything hums along, idle's fine, pop into 1st and off we go, then she starts to cough, up to about 1/2 throttle she feels to be running on only a couple of cylinders, hardly pulling me up a decent hill. Then, give the go peddle a good pump, past 1/2 way, then all seems to clear and off she accelerates like a startled rabbit. Once things get all warmed up and after a few of these episodes the engine seems to be Ok. This has happened on each of the short trips in the last few days.

I ditched the new fuel filter and replaced it, (didn't seem to have any gunk in it) it's had a dose of injector cleaner through it (original '93 injectors still fitted) all new MSD coil, dizzy, and leads....any advice on where to look next much appreciated.

Merv and Sharon · #2 (**permalink**) 05-08-2011, 11:46 PM

The throttle positioning sensor ((TPS) Greg? Do you have a spare? Or even give it a clean out. Could be sticking

Merv

byroncobra · #3 (**permalink**) 05-09-2011, 12:00 AM

Thanks Merv, I don't have a spare. I'll pull it off and check it out.

Towmaster · #4 (**permalink**) 05-09-2011, 01:02 AM

I had the same problem.... Pulled out my old Ford standard distributor (EFI) and replaced it with a shiny billet MSD distributor..... all went well till it warmed up then it would just stop. No fuel pressure when cranking. Then when it cooled down it would get fuel pressure and start again..... I took out the MSD distributor and put the standard ford distributor back in and problem solved..... So I then replaced the MSD internals with the ford internals and put it back in and it runs, even when warmed up ... but..... it misses and runs like a pig when idling around. NOt very nice to drive when you're talking 500 flywheel hp. Soooooo I took it out and put a dirty old standard Ford distributor back in and guess what.... runs like clockwork, no missing etc... Not saying it will fix yours but worth a try... and it did make 383 rwhp with the ford distributor....

Merv and Sharon · #5 (**permalink**) 05-09-2011, 01:50 AM

I had a similar scenario with a new TPS from MassFlo. In combination with the larger injectors it would not meter correctly at low settings and would not start or if it did not run smoothly, hanging idle, etc. Put the old one back in and no more problems. Greg, I do have a spare but it would easier I think for you to go to the wrecker and buy a TPS from the same or similar model and try that. If not I can post it to you.

The dizzy I am not sure about but if it is a new one .... like above, I had a new one that was rubbish and then bought the best i could get from Summit.

Rog246 · #6 (**permalink**) 05-09-2011, 02:22 AM

Greg, it might also be worth while if you're running the std ecu to get it checked out as well-it might need either some re-calibration or replacing.

Rog

Merv and Sharon · #7 (**permalink**) 05-09-2011, 03:17 AM

True. I recall recently that Rob at Tambourine had an EEC that failed. That is unusual. I sent him one of my spares and all was fine. I have another one of those too but check the TPS first.

cameron02 · #8 (**permalink**) 05-09-2011, 05:14 AM

I had a similar problem years back. I had a dodge with a 440 magnum (spec) motor. The custom headers went to some weird places due to the engine being a tight fit. They used to get real hot. The spark plug leads caught fire when running the motor in. There was so much heat that the fuel was vapourising in the lines. It went away at full throttle because there was enough flow to keep the fuel cool but when just crusing it ran like a dog. Took me ages to work out what it was. Anyway, I moved the fuel lines and fixed the problem.

byroncobra · #9 (**permalink**) 05-09-2011, 05:16 AM

Ok thanks for your input.

Towy & Merv, my engine came with no dizzy so I bought the dodgy one first, as you did Merv, had problems even starting so ditched it for the Msd. That fixed the no start. My issue is different to Towys in that once we're warmed up everything is fine. Even cold, startup is good, holds idle no problem. it loses power from idle to about half throttle, then clears with a boot full of gas.
Funny that if I stop for a minute when it coughs then proceed it seems to fix it.
I'll recheck to TPS voltage again, I have done this already on first setting up the engine. It was within specs then.
On the ECU, I read that they're pretty bulletproof, maybe that's next.

byroncobra · #10 (**permalink**) 05-09-2011, 05:22 AM

Just read your comments Cameron, wow that would have taken some lateral thinking...
My headers are real close to the rear brake lines and the thought crossed my mind that the fluid might not like the heat and lead to fading.....the fuel lines are well away from a heat source though.

Merv and Sharon · #11 (**permalink**) 05-09-2011, 05:26 AM

Still could be the TPS not being as progressive as it should be. Do you have a new fuel pressure regulator in the line?

Zedn · #12 (**permalink**) 05-09-2011, 05:30 AM

Does your ecu use a cylinder head temperature sensor? I would be looking at what ever it uses to sense engine temps.

Other things to try would be disconnecting your O2 sensor and seeing if it makes a difference and also the MAF.

suthol · #13 (**permalink**) 05-09-2011, 05:48 AM

Don't over analyze things and look at the most simple things first.

One of our clubbie guys had a car that had been going like a train but suddenly wouldn't start, he was off to buy a new starter motor.

Turned out to be an HR joint on his battery isolation switch.

Same car started to stall when turning left even with half a tank or more, must need a new pump the lad said because it sounds funny.

Funny was because it was pumping bubbles, turned out to be an in tank prefilter being clogged by the gunk that RON 98 can produce.

A quick blast with the compressor and it was smiles all round once again.

In both cases the forum help had him almost building a new car.

Another mate couldn't get a 351 to run smoothly after new plugs and leads, more wild ideas were offered.

All he'd worked on in the last 5 years were Chev.

byroncobra · #14 (**permalink**) 05-09-2011, 06:43 AM

Suthol, one learns very quickly that info kindly offered on forums is not all gonna be the best, however, I've found on many occasions that I can screw around looking for the obvious, then bung a post on a forum, and get a quick experienced opinion on finding a solution

Better go and check the in tank filter now......

Zedn · #15 (**permalink**) 05-09-2011, 06:51 AM

If it was a filter it would be the opposite.

The problem you are having most likely relates to an input to the ECU or the tuning of the ecu. If it runs ok when its warmed up then the computer is either getting an incorrect temperature input or it is not tuned correctly for below operating temp.

My 2c.

Aussie Mike · #16 (**permalink**) 05-09-2011, 06:42 PM

Might be a dodgy MAF sensor. When you are just driving around normally the ECU uses the Mass Air Flow, RPM, TPS, MAP and O2 sensors to calculate your injector pulse width. This gives the best economy, emissions drivability etc. When you stick your boot down the ECU usually goes into speed density mode where it just runs off RPM, TPS and MAP and ignores the rest. At least that's how it does on an LS1 ECU.

Cheers

Merv and Sharon · #17 (**permalink**) 05-10-2011, 02:49 AM

Any joy Greg?

byroncobra · #18 (**permalink**) 05-10-2011, 04:06 AM

ohh, I new if i'd ignore it it'd go away....
I thought i'd go for a quick run up the road to warm it up before checking sensors etc., it started and idled fine as usual, then off i went and no issues....these intermitent problems are a pain.
I ended up getting tied up on a work issue but i'll still check the operation of the TPS
when i get a chance.
Hopefully i'll get to Lakeside OK!!

Zedn · #19 (**permalink**) 05-10-2011, 05:07 AM

Ive got it!

Tighten your earth wires for your injectors. They are loose and then when the engine heats up and metal expands they work..

maybe im over analysing it.

Hopefully she stays good. Congrats again on your rego.

NASSTY · #20 (**permalink**) 05-10-2011, 08:47 AM

I'd check the positioning of your MAF. They are senitive to air flow. You want it to be in as close as a position to stock if posible. If not in stock position make sure the airflow is travelling in the right direction or try rotating the MAF and see if it improves. At WOT the EECV goes into open loop and ignores MAF so that would explain why the engine picks up after 50% throttle.