Im stumpped

[Paulscrawler78]

Hi guys I'm new here but not new to working on cars but this truck has me baffled.
Here is what I got going on
I bought a 1988 Blazer with a 5.7l it ran and I was able to drive it it had a thousand bucks worth of back registration and I had a nother 1987 Blazer that needed a motor so I swapped the motor over and for some ungodly reason it rpms up and down and will not rpm past idle Ichecked all my connections and all my voltages replaced a faulty distributor for a brand new one that came with cap rotor and module I know that the MAP sensor is causing the idle issues because when I unplug it the truck will idle fine but still will not rpm I also have to get it started by spraying Carb cleaner in the throttle body but no matter what I do I can figure out the problem for the life of me please help of u can

Thanks in advance for any and all help

 

[89Suburban]

I got to get Jim in here. Welcome aboard.

 

[Paulscrawler78]

Thank you its nice to be here but after hours of looking on this site I can't find the same issue I'm having

 

[89Suburban]

Yah, Jim is the TBI freak. He'll show up and help ya out.

 

[Paulscrawler78]

I noticed that and I look forward to his help because I've been looking at this problem cross eyed for 3 weeks and I've been working on vehicles for 15 years and I'm lost

 

[Jims86]

Hey Paul,
Welcome aboard from down below you in the Valley!
First thing that comes to mind about your starting issue...There is a purple/white striped wire that sends a starting signal to the ECM, You can check it by unplugging the large connector from the computer, and the wire is located at pin C9. the plug is numbered really small, but you can see the pin number from the side of the plug where the wires go in. Use a volt meter set for DC, and put the positive probe in the cavuty with the wire, and ground the other probe on a dash bolt. Turn the engine over a few times, and see if you get power there. If its hooked up, you should see 12v only when cranking.
And for the idle issue.
f question I have is:Was the 87 originally a 5.0?
Did the 88 run like this before the swap?
Any check engine light?
There could be a few causes. The most common is a vacuum leak. The easiest one to find and very common, is the Throttle body Gasket, and The hardest one to find, is usually the intake manifold leaks in the lifter valley. Go ahead and plug off the vac line for the brake booster, and use that carb cleaner to spray around the top of the engine after it warms up, and see if there is anything hiding that may be leaking. You also want to make sure your MAP sensor vac line is in good shape, and connected to the port on the back of the Throttle body.
When you say you disconnect the MAP, do you mean the electrical plug, or the Vac line?

 

[Paulscrawler78]

The motor seemed to be running fine before the swap but when I went to drive it from my parents in Fresno CA to my house up the hill the truck died and would only crank over and the next day I just pulled the motor out and swapped it out. And when I said I unplugged the map sensor I forgot to mention I unplugged the electrical plug I have checked for obvious vacuum leaks and sprayed the intake with the fan disconnected to search for leaks and found nothing I will check the wire you mentioned and if I read the troubleshooting PDF I found the injectors are supposed to have the same volts as the battery if so then I have an issue because the cracking volts on my battery are 9.5volts and my injector cracking volts are. .4 volts

 

[Jims86]

The motor seemed to be running fine before the swap but when I went to drive it from my parents in Fresno CA to my house up the hill the truck died and would only crank over and the next day I just pulled the motor out and swapped it out. And when I said I unplugged the map sensor I forgot to mention I unplugged the electrical plug I have checked for obvious vacuum leaks and sprayed the intake with the fan disconnected to search for leaks and found nothing I will check the wire you mentioned and if I read the troubleshooting PDF I found the injectors are supposed to have the same volts as the battery if so then I have an issue because the cracking volts on my battery are 9.5volts and my injector cracking volts are. .4 volts

The injectors are supposed to be the same as Battery power, but are supposed to be at 13 or more when the engine is running. Cranking should never be below 10 volts.
Check the wiring going tonthe starter andnmake sure nothing is loose.
So, you just swapped the 88 engine to the 87?
Again, was the 87 a 5.7 or 5.0 originally?
Just for the heck of it, if you have not already, go ahead and swap the ECM from the 88 into the 87...It may have a different calibration.

 

[Paulscrawler78]

Both trucks are the 5.7 originally I have tryed the computer swap with the same results and while the truck is running the volts are 13.x to 14.0 and all I did was a simple swap or so I thought

 

[Jims86]

Both trucks are the 5.7 originally I have tryed the computer swap with the same results and while the truck is running the volts are 13.x to 14.0 and all I did was a simple swap or so I thought

OK. hmmmmmmm. I am thinking you may have a split rubber fuel line in your tank, that runs between the pump, and the sender outlet. If you do, its pissing all the fuel pressure back into the tank, and only sending enough fuel to barely idle.
Do you have a TBI capable fuel pressure gauge?
And when you say it wont rpm past idle, you mean it wont accelerate, right?..and the idle surges?

 

[Paulscrawler78]

No I sure don't I have no clue where to even get one at I know the injectors seem to be spraying correctly both at a storage idle and full throttle

 

[89Suburban]

Can he unplug the TPS and see what happens?

 

[Paulscrawler78]

Can he unplug the TPS and see what happens?

The tps unplugged it just idles low ( while map sensor unplugged)

 

[Jims86]

Can he unplug the TPS and see what happens?

Wont matter if hes not getting a full shot from the pump.
Might want toncheck for a bent or kinked fuel line too Paul...maybe up above the trans...ya never know.

 

[Jims86]

Here is the diagram page on Gearhead.
Enjoy!
http://www.gearhead-efi.com/Fuel-In...ECM-Information-42&p=2205&viewfull=1#post2205