Engine starts and runs, surges then dies (Page 1/2)
Indyrestoproject MAY 06, 02:28 PM
I was driving along just fine when the engine started running rough and losing power. I made it home but now it's hard to start without a little starting fluid. When it does start it runs okay for a few minutes around 2000 rpm like it normally would before settling down to idle, but then it starts surging between 800 and 1300 rpm and the CEL comes on. I cleaned the IAC and have a fuel filter coming. Pressure is supposed to be between 13 and 17? I want to test the fuel pressure and see if it's the pump. I've read some of the other posts and see there could be a hose issue in the tank. Sound familiar? Any advice? Also, I noticed when I was changing vacuum lines there is a black wire at the base of the decklid about 9" long with a spade end that looks like it could be a ground wire that connects to the cruise control but I don't see a place for it. Does anyone know what this wire is for and where it is supposed to go. Thanks.
skywurz MAY 06, 02:33 PM

quote
Originally posted by Indyrestoproject:

I was driving along just fine when the engine started running rough and losing power. I made it home but now it's hard to start without a little starting fluid. When it does start it runs okay for a few minutes around 2000 rpm like it normally would before settling down to idle, but then it starts surging between 800 and 1300 rpm and the CEL comes on. I cleaned the IAC and have a fuel filter coming. Pressure is supposed to be between 13 and 17? I want to test the fuel pressure and see if it's the pump. I've read some of the other posts and see there could be a hose issue in the tank. Sound familiar? Any advice? Also, I noticed when I was changing vacuum lines there is a black wire at the base of the decklid about 9" long with a spade end that looks like it could be a ground wire that connects to the cruise control but I don't see a place for it. Does anyone know what this wire is for and where it is supposed to go. Thanks.



That wire sounds like it could be the deck lid switch. If you ground it does the trunk light (if applicable) turn on?

This sounds like fuel pump to me.
fierofool MAY 06, 02:35 PM
Tell us a little more about the car. Year, engine, transmission. That will help. The black wire may be the ground wire that goes to the metal plate attached to the underside of the decklid. It's a Radio Frequency Static eliminator ground. Stops spark plug and alternator noise on the radio. 84-87 only.

For a V6 engine, fuel pressure should be about 38-40 at idle. 43.5 not running when the key is first turned on. Not sure about the 4 cylinder pressure. That's why the particular of the car is important, but going by your username, it's an 84?
Patrick MAY 06, 03:08 PM

quote
Originally posted by fierofool:

Tell us a little more about the car. Year, engine, transmission. That will help.



What...? Fieros aren't all identical?

Yes, it's a nuisance to be expected to provide specs and/or instructions for multiple variations when basic car model info hasn't been supplied.
Indyrestoproject MAY 06, 04:09 PM
I have a 1984 SE with the 2.5L 4 cyl. and 3 speed automatic with 115K miles. I bought it 2 years ago to restore and have replaced as many of the vacuum lines as I can see, checked the EGR valve and cleaned the IAC valve. I added some FI cleaner as I had no idea how long it sat before I got it. After I put the new vacuum lines on the idle settled down and I had no problems until last week. I hadn't driven it more than 20 miles since I bought it and was running out the old gas idling the engine and driving around the block every few weeks over the winter. Last week I put in half a tank of fresh 87 octane gas and a few days later is when it started surging and the CEL came on. Is there a way to test the IAC valve? The engine is doing most of the things a bad IAC valve would do from an article I read so I'll prolly just get a new one since they are cheap unless another reason can be found for the surging idle and loss of power. Can you recommend a good brand of inline fuel pressure tester? I like the car and get lots of attention from passing neighbors. I have rebuilt, replaced or fabbed headlight motors, alternator, transmission mounts, ebrake system, rotors and pads, dogbone, bearings, seals, airbox, front speakers & baffles. Still have to do window wipes, mirror motors, front main seal, radio, AC comp., tuck up the headliner and try the p/w trick to make them faster. An LS would be nice, too. All in good time. Thanks for any ideas you have

[This message has been edited by Indyrestoproject (edited 05-06-2021).]

Indyrestoproject MAY 06, 04:31 PM
Looks like I'll have to make a new wire to connect to the decklid since there is nothing there now. No wonder the radio sounds terrible. Thanks.

[This message has been edited by Indyrestoproject (edited 05-06-2021).]

Patrick MAY 06, 05:00 PM

quote
Originally posted by Indyrestoproject:

I have a 1984 SE with the 2.5L 4 cyl... it started surging and the CEL came on. Can you recommend a good brand of inline fuel pressure tester?



What is the Trouble Code?

When I suspected my '84 was having fuel pressure issues, I used a simple cheap vacuum/pressure gauge to test it. An inline tester is nice, but it really isn't necessary to have the engine running while the fuel pressure is checked. I just disconnected the fuel line somewhere convenient ahead of the TB and connected the hose from the gauge. The two second fuel pump prime period was enough time for me to determine that the fuel pressure was too low. In my situation, the short piece of hose inside the tank had become detached. I described it all Here.
Indyrestoproject MAY 06, 08:07 PM
I have a pressure vacuum gauge but was not sure if it would be safe. I don't have a code reader but I'll ask my Bro in-law if I can use his. I think I can rig something up to check the pump pressure while it primes the system. Very good photos of the pump losing it's connector and the fix. Think I'll invest in an IAC valve anyway. Like I said I have no idea how long it sat before I got it. Kinda would like to take a look in the tank just out of curiosity. Some things on this car show it was well taken care of (Eagle GT's, exhaust header, ignition system) and others show neglect (ebrake system destroyed, crumbling vacuum lines). Nothing a little TLC and some good information like the right spec for submersible hose can't fix. I'd rather be riding down the road instead of walking with the $30 bucks I saved on something cheap. When I think of all the irreplaceable 60's muscle cars that went to the junk yard because someone didn't know how to fix them.....anyway the thread has some great info on sensors and valves and hard earned knowledge. Thanks for now.

[This message has been edited by Indyrestoproject (edited 05-06-2021).]

theogre MAY 06, 11:16 PM
L4 is 9 to 13 PSI.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

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Indyrestoproject MAY 19, 09:07 AM
Checked the vacuum and it reads 22 psi. Fuel filter is clean. Put on the new IAC vlave and it still surges. Unplugged the MAP sensor and it runs fine but dies when I put it in gear (automatic trans). I'm going to invest in a GM code reader and look for a fuel pressure gauge. Mine only goes up to 9 lbs. If the fuel pressure is low I'll go ahead and pull the tank. Probably not a bad idea anyway. Get the outside powder coated. Armor Shield the inside. What's the best brand of fuel pump? I have a new ignition module to put on. Good to still be able to get spare parts cheap. Plugs and an oil change won't hurt. O2 sensor, MAP and MAF sensors are all that's left to replace? Are there ways to test these? Anything else I can check? Maybe clean out the throttle body? Thanks.

[This message has been edited by Indyrestoproject (edited 05-19-2021).]