I've got an EFI question if anyone can help me with. 88 EFI 5.0 system on a 74 early bronco engine. It has a very slight hesitation on cold drive away. Not really bad, only when I need to pull into traffic rather quick. when it warms up its o.k. Is it normal to have a slight hesitation when cold? I do let it run a couple of minutes before driving off. I was told that EEC-IV systems are suppose to have great throttle response from cold to hot? I've checked my TPS voltage at idle (.89v) with no dead spots. My air injection/ and EGR has been disconnected and vac. lines plugged. ECT sensor seems to be in specs with the temp. The only thing odd is my system came with 14# (grey top) injectors with it. I am planning to install 19# injectors as soon as I recieve them. I don't think the injectors would cause this would it? I appreciate any replies,thanks
Mike

 

Check the IAC (idle air controler) they tend to plug up a little, and it may need to be cleaned or replaced.

 

Where is the timing set with the spout connector unplugged? The ecm/speed density system is calibrated for the grey top injectors. It may run a bit rich with the 19# injectors. The HO engines with roller cams and better exhaust came with the 19# injectors. Does your conversion have mass-air?

 

I did clean Iac prior to installing. I also unplugged the connector to the Iac when cold to see if idle drops off (It does).
Lxman, base timing set at 10 deg (spout unplugged). Funny you mentioned 14# should be in because several months ago I posted a ? on injectors and several people said It suppose to be yellow tops (#19)?? I've checked my friends 89 truck 5.0 and it has yellows.
Let me tell you the origin of my parts as it may help with your advice (because I really need it). I bought the complete efi set-up on e-bay. Seller claims from 87 5.0 non-HO? He sent in 2 seperate boxes to split shipping weight. 1st box recieved containing up&lower intakes. Idle valve broken off and egr and intake passages choked with crud. 2nd box was lost for 5 weeks. It contained wire harness, ECU,dist.,fuel lines, and 7 yellow top inj. and 8 grey inj with lots of carbon build-up. My seller wasn't sure which were original. In between that time and pacing back and forth, I found a upper/lower intake from a 88 mk7 with a 5.0 HO MAP, but it had these funny all black injectors with flat tips? but the intakes were much cleaner and the t/body moved more freely. I also came across a set of know good grey top inj. from a 88 5.0 cougar. My second box finally came. So I'm using a 88 mk7 u/lwr intake (which seems no different from the others), grey top injectors from the 88 cougar, and ECU, wire harness, relays and everything else from the 87 5.0.
Sorry for the long story but I wanted to furnish as much info as possible.
any suggestions is appreciated.

 

I know most car non-HO engines had white injectors. The Mustangs and Mark VII's had Yellow. I think that the trucks had yellow as well.
The HO and non HO intakes are the same (cars). The 87-up Mustangs had a 60mm TB and the others use a 55mm I believe.
Is the ECM supposed to be from a truck? If so, then use the yellow(19#) injectors.

 

The seller said the ECM is from an 87 mk7. The code # on it is EC1. Do you know where I can find a reference as to what ECM uses which injectors? Also do you think that my slight hesitation is injector related?

 

Lxman, You were right about it running rich. Yesterday I just finished installing the 19# inj. and it ran like crap. Idle would wander up and down and black smoke started coming from the tail pipe. I inspected my s/plugs and they all were covered with carbon. It eventually stalled and would not idle, I had to keep it above 1500 rpm. This morning I rechecked all my vacuum lines and did a self-test and ER to get some codes. Codes 92/42 (Rt side O2 rich/O2 always reading rich). I just so happened had a ECM from a 88 HO. I connected it and started the truck, it ran crappy at first but what-do-u-know, the idle started to settle down. After a few minutes it ran really smooth, I guess the plugs were starting to clean up.
This fuel inj swap has been a challenge from day one for a carb guy like me. I've always thought an ECM 5.0 sfi were all the same. I've learned 2 things from this experience. Speed-density ECMs are not all the same and are calibrated to their matching components and If doing a EFI retro swap, try to get it all the parts from a one known running engine so you don't mix-match parts. I now wish I had gone mass-air but one was not avail. at that time.
It now runs fine and I don't have the hesitation anymore. I now realize the neck snapping throttle response EFI has over carb! I do want to thank you guys for all the response in walking me through this, I couldn't have done it without you guys.... Thanks again

 

Glad to hear you got it fixed. It's amazing what a small calibration change can do

 

I don't know about the TPS on a density car but I have owend and raced many fast mass air cars and we run the TPS at .97-.99 and 1.0+ on blown cars.